WO2001085981A2 - Methodes de stimulation de la regeneration et de la reparation du systeme nerveux par regulation de l'activite de l'arginase 1 et de la synthese des polyamines - Google Patents

Methodes de stimulation de la regeneration et de la reparation du systeme nerveux par regulation de l'activite de l'arginase 1 et de la synthese des polyamines Download PDF

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WO2001085981A2
WO2001085981A2 PCT/US2001/014364 US0114364W WO0185981A2 WO 2001085981 A2 WO2001085981 A2 WO 2001085981A2 US 0114364 W US0114364 W US 0114364W WO 0185981 A2 WO0185981 A2 WO 0185981A2
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arginase
growth
composition
mag
neuron
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PCT/US2001/014364
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WO2001085981A3 (fr
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Marie T. Filbin
Rajiv R. Ratan
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Research Foundation Of City University Of New York
Beth Israel Deaconess Medical Center
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Priority to AU5945301A priority Critical patent/AU5945301A/xx
Priority to AU2001259453A priority patent/AU2001259453B2/en
Priority to CA002408255A priority patent/CA2408255A1/fr
Priority to EP01932977A priority patent/EP1278537B1/fr
Priority to DE60137414T priority patent/DE60137414D1/de
Priority to US10/275,513 priority patent/US7741310B2/en
Publication of WO2001085981A2 publication Critical patent/WO2001085981A2/fr
Publication of WO2001085981A3 publication Critical patent/WO2001085981A3/fr
Priority to HK03105409.1A priority patent/HK1054680A1/zh
Priority to US12/613,310 priority patent/US8673594B2/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61K31/00—Medicinal preparations containing organic active ingredients
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    • A61K31/7042—Compounds having saccharide radicals and heterocyclic rings
    • A61K31/7052—Compounds having saccharide radicals and heterocyclic rings having nitrogen as a ring hetero atom, e.g. nucleosides, nucleotides
    • A61K31/706—Compounds having saccharide radicals and heterocyclic rings having nitrogen as a ring hetero atom, e.g. nucleosides, nucleotides containing six-membered rings with nitrogen as a ring hetero atom
    • A61K31/7064—Compounds having saccharide radicals and heterocyclic rings having nitrogen as a ring hetero atom, e.g. nucleosides, nucleotides containing six-membered rings with nitrogen as a ring hetero atom containing condensed or non-condensed pyrimidines
    • A61K31/7076—Compounds having saccharide radicals and heterocyclic rings having nitrogen as a ring hetero atom, e.g. nucleosides, nucleotides containing six-membered rings with nitrogen as a ring hetero atom containing condensed or non-condensed pyrimidines containing purines, e.g. adenosine, adenylic acid
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61K31/00—Medicinal preparations containing organic active ingredients
    • A—HUMAN NECESSITIES
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    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K31/00—Medicinal preparations containing organic active ingredients
    • A61K31/557—Eicosanoids, e.g. leukotrienes or prostaglandins
    • A61K31/5575—Eicosanoids, e.g. leukotrienes or prostaglandins having a cyclopentane, e.g. prostaglandin E2, prostaglandin F2-alpha
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61K38/17—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
    • A61K38/18—Growth factors; Growth regulators
    • A61K38/185—Nerve growth factor [NGF]; Brain derived neurotrophic factor [BDNF]; Ciliary neurotrophic factor [CNTF]; Glial derived neurotrophic factor [GDNF]; Neurotrophins, e.g. NT-3
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K38/00—Medicinal preparations containing peptides
    • A61K38/16—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • A61K38/43—Enzymes; Proenzymes; Derivatives thereof
    • A61K38/46—Hydrolases (3)
    • A61K38/50—Hydrolases (3) acting on carbon-nitrogen bonds, other than peptide bonds (3.5), e.g. asparaginase
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P25/00—Drugs for disorders of the nervous system
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    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P25/00—Drugs for disorders of the nervous system
    • A61P25/14—Drugs for disorders of the nervous system for treating abnormal movements, e.g. chorea, dyskinesia
    • A61P25/16—Anti-Parkinson drugs
    • A—HUMAN NECESSITIES
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    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P25/00—Drugs for disorders of the nervous system
    • A61P25/28—Drugs for disorders of the nervous system for treating neurodegenerative disorders of the central nervous system, e.g. nootropic agents, cognition enhancers, drugs for treating Alzheimer's disease or other forms of dementia
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
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    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/5005—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells
    • G01N33/5008—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells for testing or evaluating the effect of chemical or biological compounds, e.g. drugs, cosmetics
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/5005—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells
    • G01N33/5008—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells for testing or evaluating the effect of chemical or biological compounds, e.g. drugs, cosmetics
    • G01N33/502—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells for testing or evaluating the effect of chemical or biological compounds, e.g. drugs, cosmetics for testing non-proliferative effects
    • G01N33/5026—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells for testing or evaluating the effect of chemical or biological compounds, e.g. drugs, cosmetics for testing non-proliferative effects on cell morphology
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/5005—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells
    • G01N33/5008—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells for testing or evaluating the effect of chemical or biological compounds, e.g. drugs, cosmetics
    • G01N33/5044—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving human or animal cells for testing or evaluating the effect of chemical or biological compounds, e.g. drugs, cosmetics involving specific cell types
    • G01N33/5058—Neurological cells
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    • G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
    • G01N2333/435—Assays involving biological materials from specific organisms or of a specific nature from animals; from humans
    • G01N2333/475—Assays involving growth factors

Definitions

  • This invention relates to the novel identification of arginase as an enzymatic activity which can reverse inhibition of neuronal regeneration in the central and peripheral nervous system. Assays to monitor the effects of various agents on arginase expression and thus on neuronal regeneration and repair and to identify agents which will block or promote the inhibitory effects on neuronal outgrowth are provided. This invention also relates to compositions and methods using agents that can reverse the inhibitory effects of myelin on neural regeneration by affecting arginase activity or putrescine and derivative polyamine levels in a neuron.
  • Methods for regulating and for promoting (or repressing) neuronal growth or regeneration in the nervous system comprising the step of administering at least one of the compositions according to this invention.
  • the adult, mammalian central nervous system (CNS) does not regenerate after injury despite the fact that there are many molecules present which promote nerve and axonal growth.
  • the adult, mammalian peripheral nervous system 5 (PNS) in contrast, does regenerate to some extent. It is believed that the lack of regeneration in the CNS is caused by the presence of molecules which actively prevent or inhibit regeneration.
  • cAMP levels may play an important role in regulating the capacity of a neuron to undergo axonal regeneration.
  • Downstream effectors which are directly responsible for improved neuronal growth on myelin remain unknown.
  • One candidate may be polyamines, such as spermidine and spermine, and their diamine precursor putrescine, which are ubiquitously distributed in prokaryotic and eukaryotic cells and eukaryotic tissues.
  • Polyamines are involved in a large number of cellular functions, including many which involve nucleic acids, such as DNA replication, gene expression and peptide synthesis.
  • nucleic acids such as DNA replication, gene expression and peptide synthesis.
  • Polyamines have been shown in some systems to be essential for cell proliferation and differentiation during wound healing. We considered it possible that, because polyamines are important in tissue wound healing, they may also function in axonal regeneration in the nervous system, which can occur with or without concomitant cell proliferation.
  • Polyamines are abundant in the mammalian nervous system (see, e.g., Bernstein et al., Prog. Neurobiol.. 57(5), pp. 485-505 (1999)). And, polyamines have been shown to promote neurite regeneration of injured axons in cultured rat hippocampal neurons (Chu et al., Brain Res.. 673, pp. 233-241 (1995)). Exogenous polyamine treatment has been reported to accelerate axonal regeneration and functional recovery of crushed peripheral (rat sciatic and facial) nerves (Dornay et al., Exp. NeuroL 92, pp. 665-674 (1986); Kauppila et al., Exp. Neuro 99, pp.
  • Polyamines are therefore candidates for molecules which act in a cAMP-mediated signaling pathway to regulate neural regenerative capacity in the presence of myelin inhibitors.
  • Polyamines in mammalian cells are synthesized from the amino acid arginine in a pathway involving at least three catalytic steps. (See Figure 1 for a schematic diagram of polyamine synthesis). The first step in polyamine synthesis is conversion of arginine to ornithine and urea, catalyzed by the enzyme arginase.
  • Ornithine is converted to putrescine (a diamine) by the enzyme ornithine decarboxylase (ODC), a rate-limiting enzyme in polyamine synthesis (Shantz, L.M. and Pegg, A.E., Int. I Biochem. Cell Biol.; 31(1), pp. 107-122 (1999); Wu, G. and Morris, S.M., Jr., Biochem. J.. 336, pp. 1-17 (1998)).
  • Putrescine in turn, is the precursor to the polyamine spermidine, which can be converted to a variety of other polyamines, such as spermine (see Figure 1).
  • ornithine decarboxylase ODC
  • arginase may regulate the availability of ornithine for polyamine synthesis despite the observation that conversion of ornithine to putrescine by ODC is the rate-limiting step in polyamine synthesis. Further support for this notion comes from observations that certain cells deficient in arginase cannot proliferate unless polyamines or ornithine are provided.
  • arginase activity is severely deficient in endothelial cells of the diabetic BB rat (an animal model of human type I diabetes mellitus) (Wu and Meninger, Am. J. Physiol. Heart Circ. Physiol.. 265, H1965-H1971 (1993)), and these cells exhibit a marked impairment in proliferation (Meninger et al., J. Vase. Research. 33 (SI): 66 (1996)). Correlations between arginase activity and polyamine synthesis also been observed in kidney and intestine. A causal relationship between arginase activity and polyamine synthesis has not, however, been established.
  • Arginase genes are found in bacteria, fungi, plants and animals. Two isoforms of arginase encoded by separate genes have been identified in mammalian cells (Shi et al., Mammalian Genome. 9, pp. 822-824 (1998); incorporated herein by reference). The two isoforms of arginase differ in molecular and immunological properties, tissue distribution, subcellular location, and regulation of expression.
  • Type I arginase (arginase I) is a cytosolic enzyme which is highly expressed in liver and detected in only a few other tissues. Its main, but not its only, role is as a component of the urea cycle.
  • Type II arginase is a mitochondrial enzyme which is expressed to varying degrees in a number of tissues but with little or no expression detectable in liver.
  • One of the functions of arginase II is to regulate nitric oxide (NO) levels by competing with nitric oxide synthetase for arginine, the availability of which is one of the rate-limiting factors in cellular NO production (Gotoh and Mori, J. Cell Biol. 144, pp. 427-434 (1999)).
  • NO is important in the nervous system as a signaling molecule involved in cell survival, memory, and cell differentiation.
  • Arginase I and LI are approximately 70% identical at the amino acid sequence level and differ primarily in that arginase II has a mitochondrial protein targeting sequence. (See, e.g., Morris et al., Gene. 193, pp. 157-161 (1997); incorporated herein by reference). A comparison of arginase sequences from the livers of rat, human, Xenopus laevis, yeast and Agrobacterium TiC58 plasmid has revealed three conserved histidine residues.
  • arginase I and arginase II are similar but distinguishable because arginase II is not as susceptible to feedback inhibition by ornithine as is arginase I. There is reason to believe that arginase II, like arginase I, can increase cytosolic polyamines by increasing mitochondrial ornithine, which is then transported back to the cytosol. (See Jenkinson et al., Comparative properties of arginases, Comp.Biochem. Physiol., 114B, pp. 107-132 (1996)). Arginase I and ⁇ are induced in murine macrophage cell lines by cAMP.
  • the present invention solves the problems referred to above by identifying arginase as an enzyme whose activity can reverse inhibition by myelin of neural regeneration in the central and peripheral nervous system.
  • cAMP induces arginase polynucleotide and polypeptides levels in neurons.
  • CNS central nervous system
  • arginase over-expression in nerve cells is sufficient to increase polyamines to levels which relieve inhibition of neuronal regeneration by myelin and myelin inhibitors such as MAG.
  • the present invention provides a composition comprising an agent which can overcome myelin-dependent growth regulation of a neuron by affecting the endogenous levels of polyamines (such as spermidine or spermine, or the precursor putrescine) in the neuron.
  • the agent increases polyamines in a particular neuron at a particular developmental stage to a level which overcomes myelin-dependent growth regulation.
  • the agent decreases polyamines in a particular neuron at a particular developmental stage to a level which overcomes myelin-dependent growth regulation.
  • the agent affects the endogenous level of putrescine and putrescine-derived polyamines in a neuron.
  • the present invention also provides a composition comprising an arginase modulatory agent which increases the biological activity of arginase in a neuron (i.e., is a neuronal arginase agonist), in an amount effective for altering neuronal growth or regeneration.
  • the arginase agonist comprises a nucleic acid molecule which, upon expression in a neuron, can increase the biological activity of arginase.
  • the agent comprises a nucleic acid molecule which encodes arginase, or muteins, analogs, fusions or fragments thereof, having arginase biological activity in a neuron.
  • the agent comprises a non-arginase encoding nucleic acid molecule which, upon expression, increases the arginase biological activity in a neuron.
  • the arginase agonist is a protein or small molecule which increases the arginase biological activity in a neuron.
  • the arginase agonist is selected from the group consisting of TGF ⁇ , LL4, LLIO and PGE2.
  • the agent comprises a trophic factor.
  • the trophic factor is selected from the group consisting of a neurotrophin, EGF, PDGF, bFGF, neuroregulin (also known as aria, GGF or neu), oncostatin M and LLF1.
  • the trophic factor is a neurotrophin selected from the group consisting of BDNF, GDNF, NGF, NT3, NT4 (NT4/5), IGF1, CNTF and galanin. More preferably, the neurotrophin is selected from the group consisting of BDNF, GDNF, NGF, NT3 and NT4 (NT4/5), and most preferably, is BDNF or GDNF.
  • the arginase agonist is a substance which increases cAMP levels in a neuron.
  • the substance is a non-hydrolyzable cAMP analog, such as dibutyryl cAMP or Sp-cAMP.
  • the present invention also provides a composition comprising an arginase modulatory agent which decreases the biological activity of arginase in a neuron (i.e., a neuronal arginase antagonist) in an amount effective for altering neural growth or regeneration.
  • the agent comprises a nucleic acid molecule which, upon expression in a neuron, can decrease the biological activity of arginase.
  • the agent comprises a nucleic acid molecule which encodes an arginase antagonist, such as an antisense RNA or other hybrid nucleic acid, or a mutein, analog, fusion or fragment of arginase that inhibits endogenous arginase biological activity in a neuron.
  • the agent comprises a non-arginase encoding nucleic acid molecule which, upon expression, decreases the arginase biological activity in a neuron.
  • the arginase antagonist is a protein or small molecule which decreases the arginase biological activity in a neuron, such as a protein kinase A inhibitor.
  • the present invention also provides a method for relieving (in part or in full) inhibition by myelin or MAG of neuronal growth or regeneration by altering endogenous polyamine levels; and a method for relieving (in part or in full) inhibition by myelin or MAG of neuronal growth or regeneration by altering arginase bioactivity in a neuron, each comprising the step of administering, in a manner which can affect the nervous system, a composition of the invention.
  • Methods for regulating neural growth or regeneration in the nervous system comprising the step of administering, in a manner which can affect the nervous system, a composition of the invention, are also provided.
  • each of the methods further comprises the step of monitoring the growth of a neuron after the step of administering the composition.
  • the present invention provides an assay for determining whether neurite outgrowth from a particular type of neuron at a particular age is stimulated or inhibited in the presence of myelin or MAG and an arginase modulatory agent.
  • the method comprises the steps of: a) culturing a first sample of a selected neuronal cell type on a growth- permissive substrate comprising purified myelin; b) culturing a second sample of the selected neuronal cell type on a growth- permissive substrate comprising purified myelin and at least one added arginase modulatory agent; and c) comparing the relative amount of neurite growth in the cultured cells of a) and b); wherein when the relative growth of neurites in the cultured cells of b) is greater than in a), neurite outgrowth from the selected neuronal cell type is stimulated by the arginase modulatory agent in the presence of myelin; and when the relative growth of neurites in the cultured cells of b) is less than in a), neurite outgrowth from the selected neuronal cell type is inhibited by the arginase modulatory agent in the presence of myelin.
  • the one or more arginase modulatory agents may be added before, after, or simultaneously with addition of myelin to the selected neuronal cells.
  • the myelin is myelin purified from the central nervous system (CNS).
  • the method comprises the steps of: a) culturing a first sample of a selected neuronal cell type on a growth- permissive substrate comprising MAG; b) culturing a second sample of the selected neuronal cell type on a growth- permissive substrate comprising MAG and at least one added arginase modulatory agent; and c) comparing the relative amount of neurite growth in the cultured cells of a) and b); wherein when the relative growth of neurites in the cultured cells of b) is greater than in a), neurite outgrowth from the selected neuronal cell type is stimulated by the arginase modulatory agent in the presence of MAG; and when the relative growth of neurites in the cultured cells of b) is less than in
  • the one or more arginase modulatory agents may be added before, after, or simultaneously with addition of MAG to the selected neuronal cells.
  • the growth-permissive substrate comprising MAG is a surface comprising bound MAG molecules. More preferably, the surface is a cell engineered to produce cell surface MAG. In another preferred embodiment, the growth-permissive substrate comprises soluble forms of MAG.
  • Figure 2 Improved Axonal Growth on MAG Induced By Elevating cAMP Levels is Transcription-Dependent.
  • A Isolated cerebellar neurons at a density of
  • 20,000 neurons per well were plated onto a monolayer of either MAG-expressing Chinese hamster ovary (CHO) cells (striped bars) or control CHO cells (black bars) and cultured overnight before being fixed and immunostained for GAP43 to visualize the neurites.
  • dibutyryl cAMP (dbcA) at 1 mM in the presence or absence of the inhibitor of transcription, 5,6- dichloro-1-b-D-ribofuranosylbenzimidazole (DRB) at 5 ⁇ M was added to each culture.
  • FIG. 1 Isolated cerebellar neurons at a density of 20,000 neurons per well were plated onto a substrate of purified CNS myelin and cultured overnight before being fixed and immunostained for GAP43. The length of the longest neurite per neuron from 180-200 neurons was measured and results are the average length +/- SEM.
  • dibutyryl cAMP (dbcA) at 1 mM in the presence or absence of the inhibitor of transcription, 5,6-dichloro-l-b-D- ribofuranosylbenzimidazole (DRB) at 5 ⁇ M, was added to each culture.
  • DRB 5,6-dichloro-l-b-D- ribofuranosylbenzimidazole
  • Cerebellar neurons (1 x 10 6 ) were plated onto poly-L-lysine and cultured overnight with brain-derived neurotrophic factor (BDNF) at 200 ng/ml, (termed priming) in the presence or absence of DRB at 5 ⁇ M, before being transferred to the CNS myelin substrate.
  • BDNF brain-derived neurotrophic factor
  • Figure 4 Priming Neurons With Brain Derived Neurotrophic Factor (BDNF) or Dibutyryl (db) cAMP Up-Regulates Arginase I RNA Levels In Cerebellar Neurons.
  • RNA isolated from cerebellar neurons without treatment (lane 2), from cerebellar neurons exposed overnight to either BDNF (200 ng/ml) (lane 3) or dbcAMP (1 mM) (lane 4), was reverse transcribed and subjected to (A) semi- quantitative PCR; or (B) quantitative PCR; using primers specific for arginase I.
  • RNA isolated from liver tissue was subjected to RT-PCR and quantitative PCR procedures using the same primers ((A), lane 1; (B), "Liver")
  • Figure 5 Arginase I Protein Is Up-Regulated In Cerebellar Neurons After Treating with dbcAMP, BDNF or GDNF For Various Times. Cerebellar neurons were untreated (-) or exposed to either (A) 200 ng/ml BDNF or (B) lmM dbcAMP for 1 hour (h), 3h, 21h or 24h; or (C) 200 ng/ml GDNF (+) for lh, 3h or 5h and the cells lysed in the presence of protease inhibitors.
  • Cerebellar neurons were plated onto (A) MAG-expressing CHO (striped bars) or control CHO (black bars) cells; or (B) a substrate of purified CNS myelin, in the presence (+) or absence (-) of 1 mM dbcAMP (dbcA) and/or 1 mM DL-a- difluoromethyl-ornithinehydrochloride (DFMO), and cultured overnight before being fixed and immunostained for GAP43. The longest neurite from at least 180-200 neurons were measured. Results are shown as the mean neurite length +/- SEM.
  • FIG. 7 An Inhibitor of ODC Blocks the Priming Effects of BDNF on the Inhibition by MAG Or Myelin and Putrescine Restores It. Cerebellar neurons were primed overnight with or without BDNF (200 ng/ml), in the presence or absence of DFMO (1 mM), with or without putrescine (10 ⁇ M), before being transferred to (A) MAG-expressing (striped bars) or control (black bars) CHO cells; or (B) a substrate of purified CNS myelin. After further incubation, neurons were fixed and immunostained for GAP43. The longest neurite from each neuron for 180-200 neurons were measured. Results are shown as the mean neurite length +/- SEM.
  • FIG 8 An Inhibitor Of ODC Blocks The Priming Effects Of GDNF On The Inhibition By MAG. Cerebellar neurons were primed overnight with (+) or without (-) GDNF (200 ng/ml) in the presence (+) or absence (-) of DFMO (1 mM) before being transferred to MAG-expressing (striped bars) or control (black bars) CHO cells. After further incubation, neurons were fixed and immunostained for GAP43. The longest neurite from each neuron for 180-200 neurons were measured. Results are shown as the mean neurite length ⁇ SEM. Figure 9: Putrescine Treatment Alone Is Sufficient To Overcome Inhibition And Allow Subsequent Growth on MAG or Myelin.
  • Cerebellar neurons were primed overnight with putrescine at increasing concentrations ranging from 0 - 100 ⁇ M. Primed neurons were transferred to either MAG-expressing or control CHO cells (A) or a substrate of CNS myelin (B) for further incubation. Neurons were then fixed and immunostained for GAP43. The longest neurite from each neuron was measured for 180-200 neurons. Results are shown as the percentage of control. (A) 100% is the average neurite length +/- SEM of neurons primed without putrescine and subsequently grown on control CHO cells. (B) 100% is the average neurite length +/- SEM. of neurons primed without putrescine and subsequently grown on CNS myelin substrate. Figure 10: Arginase Expression Increases After A Conditioning Lesion To
  • DRG Dorsal root ganglial
  • DFMO Myelin Is Blocked By The ODC Inhibitor, DFMO.
  • Postnatal day 1 (PI) DRG neurons were isolated and plated on MAG-expressing (stippled bars) or control (black bars) CHO cells, with (+) or without (-) 1 mM DFMO. After overnight incubation, neurons were fixed and immunostained for GAP 43. The longest neurite from each of
  • Adenovirus-Mediated Gene Transfer Is Sufficient To Overcome Inhibition By MAG.
  • Postnatal day 5 DRG neurons (0.5 x 10 6 ) were plated in 24-well plates and infected with adenovirus containing ArgL-GFP or GFP alone. After overnight culture, infected neurons were transferred to MAG-expressing (stippled bars) or control (black bars) CHO cells for neurite outgrowth. Neurons were fixed and immunostained for GAP43. The neurons with double staining of GAP43 and GFP were considered as positively infected. The length of the longest neurite per neuron was measured for 120-150 positively infected neurons. Results are shown as the average neurite length +/- SEM of GFP-infected (GFP) or Argl-infected (Argl) neurons grown on MAG.
  • Enzymatic reactions and cell culture and purification techniques are performed according to manufacturer's specifications, as commonly accomplished in the art or as described herein.
  • the nomenclatures used in connection with, and the laboratory procedures and techniques of, analytical chemistry, synthetic organic chemistry, and medicinal and pharmaceutical chemistry described herein are those well known and commonly used in the art. Standard techniques are used for chemical syntheses, chemical analyses, pharmaceutical preparation, formulation, and delivery, and treatment of patients.
  • arginase refers to an enzyme that is capable of catalyzing conversion of the amino acid arginine (arg) to ornithine. Such conversion may be assessed by any of a number of methods well known to those of skill in the art, including enzymatic assays using a labeled or otherwise detectable substrate.
  • an arginase is derived from a mammalian cell, e.g., rat, mouse, bovine or human.
  • an arginase is derived by expression of a polynucleotide derived from a mammalian cell, e.g., rat, mouse, bovine or human, such as from: a) the human Argl liver polynucleotide sequence (GenBank
  • the arginase is derived by expression of a polynucleotide derived from a mammalian neuron or glial cell.
  • arginase activity refers to an enzymatic activity of an arginase, or a mutein, homologous protein, analog, derivative, fusion or fragment thereof, that catalyzes the conversion of arginine (arg) to ornithine.
  • Arginase enzymatic assays are well known to those of skill in the art.
  • a characteristic of arginase activity e.g., association and dissociation constants, catalytic rates and substrate turnover rates, is the same as that characteristic possessed by the arginase expressed from the human Argl liver polynucleotide sequence (GenBank Accession No. NM 000045 and references cited therein).
  • the arginase activity is different from that of an arginase expressed from the human Argl liver polynucleotide sequence (GenBank Accession No. NM 000045 and references cited therein).
  • An arginase activity that is different may be one, e.g., that has an increase or decrease in catalytic activity or that has a different association and/or dissociation constant compared to that of an arginase expressed from the human Argl liver polynucleotide sequence (GenBank Accession No. NM 000045 and references cited therein).
  • An agent which alters or modulates the arginase "activity", “bioactivity” or “biological activity” in a neuron refers to an agent which can directly or ultimately increase (agonist) or decrease (antagonist) arginase enzymatic activity (the conversion of arginine to ornithine), or the immediately measurable results of such activity (e.g., increased ornithine and derivative polyamine synthesis) in a neuron.
  • Arginase activity may be modulated by altering levels of DNA, RNA or protein encoding arginase or an arginase modulatory agent in a neuron.
  • Arginase activity may also be modulated by mutation or alteration of an arginase polynucleotide or polypeptide molecule directly.
  • Such mutations or alterations include, but are not limited to, those which alter a substrate affinity constant or binding rate, a substrate dissociation rate, the catalytic or turnover rate of the enzyme, and the binding constant of an arginase subunit to another homologous or heterologous subunit or molecule which affects (increases or decreases) catalysis by the arginase molecule.
  • Arginase activity in a neuron may also be modulated by association (covalent or non-covalent) with another agent or factor.
  • Arginase activity may be measured directly by arginase specific enzymatic assays (infra) or indirectly by assaying arginase encoding nucleic acid levels in a cell (e.g., by RT-PCR, Northern blot analysis or other methods for measuring levels of steady-state RNA encoding arginase), or arginase specific protein molecules in a cell (e.g., by a variety of immunoaffinity procedures, including Western blot techniques, ELISA assays and the like) — all of which are techniques that are well- known to those of skill in the art and which are described herein.
  • the arginase activity to be modulated according to the invention may be expressed from a wild-type (endogenous or exogenous) polynucleotide or polypeptide encoding arginase.
  • the activity may also be expressed from a modified polynucleotide or protein encoding arginase, including but not limited to muteins, analogs, fusions or fragments thereof having arginase biological activity in a neuron.
  • axonal growth or “axonal regeneration” as used herein refer both to the ability of an axon to grow and to the ability of an axon to sprout.
  • An axon sprout is defined as a new process that extends from an existing or growing axon. (See, e.g., Ma et al, Nat. Neurosci.. 2, pp. 24-30 (1999), which is incorporated herein by reference).
  • MAG refers to myelin-associated glycoprotein, which is a molecule derived from myelin which promotes or inhibits neuronal growth and regeneration in the CNS and PNS depending on the cell type and the developmental stage of the neuron.
  • the term “MAG” also refers to a "MAG derivative", which is a molecule comprising at least one MAG extracellular domain, wherein the MAG molecule has been altered (e.g., by recombinant DNA techniques to make chimera with portions of other molecules fused to the MAG molecule, or by chemical or enzymatic modification) or mutated (e.g., internal deletions, insertions, rearrangements and point mutations).
  • MAG derivatives unless otherwise noted, retain MAG activity.
  • MAG bioactivity and "MAG biological activity” refer to the ability of a molecule, especially an altered or mutant form of MAG, to inhibit or promote neurite outgrowth of a selected neuronal cell type of a particular age, as detected in a neurite outgrowth assay such as those described herein, in qualitatively the same direction as cell-surface or soluble MAG.
  • MAG binding activity refers to the ability of a molecule, especially an altered or mutant form of MAG, to compete with cell-surface MAG or soluble MAG for sialic-acid dependent neuron binding in an assay such as those described herein. For example, preferred inhibitors of MAG retain MAG binding activity but have reduced or absent MAG bioactivity.
  • MAG activity refers generically to MAG bioactivity and binding activity as described above.
  • polynucleotide or “nucleic acid molecule” refers to a polymeric form of nucleotides of at least 15 bases in length, either ribonucleotides or deoxynucleotides or a modified form of either type of nucleotide.
  • the term includes single- and double-stranded forms of DNA and RNA, and sense or antisense orientations with respect to coding sequences.
  • a polynucleotide may include either or both naturally-occurring and modified nucleotides linked together by naturally-occurring and/or non-naturally occurring nucleotide linkages.
  • nucleotide linkages includes nucleotides linkages such as phosphorothioate, phosphorodithioate, phosphoroselenoate, phosphorodiselenoate, phosphoroanilothioate, phoshoraniladate, phosphoroamidate, and the like. See e.g., LaPlanche et al. Nucl. Acids Res.
  • allelic variant refers to one of two or more alternative naturally-occurring forms of a gene, wherein each gene possesses a unique nucleotide sequence.
  • different alleles of a given gene have similar or identical biological properties.
  • the left hand end of a polynucleotide sequence in sense orientation is the 5' end and the right hand end of the sequence is the 3' end.
  • the left hand direction of a polynucleotide sequence in sense orientation is referred to as the 5' direction
  • the right hand direction of the polynucleotide sequence is referred to as the 3' direction.
  • sequence identity refers to the residues in the two sequences which are the same when aligned for maximum correspondence.
  • the length of sequence identity comparison may be over a stretch of at least about nine nucleotides, usually at least about 20 nucleotides, more usually at least about 24 nucleotides, typically at least about 28 nucleotides, more typically at least about 32 nucleotides, and preferably at least about 36 or more nucleotides.
  • polynucleotide sequences can be compared using FASTA, BLAST, Gap or Bestfit, which are software programs in Wisconsin Package Version 10.0, Genetics Computer Group (GCG), Madison, Wisconsin.
  • FASTA provides alignments and percent sequence identity of the regions of the best overlap between the query and search sequences (Pearson, 1990, herein incorporated by reference).
  • percent sequence identity between nucleic acid sequences can be determined using FASTA with its default parameters (a word size of 6 and the NOP AM factor for the scoring matrix) or using Gap with its default parameters as provided in GCG Version 6.1, herein incorporated by reference.
  • nucleic acid or fragment thereof indicates that, when optimally aligned with appropriate nucleotide insertions or deletions with another nucleic acid (or its complementary strand), there is nucleotide sequence identity in at least about 55%, more preferably 60% of the nucleotide bases, usually at least about 70%, more usually at least about 80%, preferably at least about 90%, and more preferably at least about 95-98% of the nucleotide bases, as measured by any well-known algorithm of sequence identity, such as FASTA, BLAST or Gap, as discussed above.
  • nucleic acid or fragment thereof hybridizes to another nucleic acid, to a strand of another nucleic acid, or to the complementary strand thereof, under selective hybridization conditions.
  • selective hybridization will occur when there is at least about 55% sequence identity ⁇ preferably at least about 65%, more preferably at least about 75%, and most preferably at least about 90% ⁇ over a stretch of at least about 14 nucleotides. See, e.g., Kanehisa, Nucleic Acids Res.. 12, pp. 203-13, (1984), incorporated herein by reference.
  • Nucleic acid hybridization will be affected by such conditions as salt concentration, temperature, solvents, the base composition of the hybridizing species, length of the complementary regions, and the number of nucleotide base mismatches between the hybridizing nucleic acids, as will be readily appreciated by those skilled in the art.
  • Stringent hybridization conditions and “stringent wash conditions” in the context of nucleic acid hybridization experiments depend upon a number of different physical parameters. The most important parameters include temperature of hybridization, base composition of the nucleic acids, salt concentration and length of the nucleic acid. One having ordinary skill in the art knows how to vary these parameters to achieve a particular stringency of hybridization.
  • stringent hybridization is performed at about 25°C below the thermal melting point (Tm) for the specific DNA hybrid under a particular set of conditions.
  • Stringent washing is performed at temperatures about 5°C lower than the Tm for the specific DNA hybrid under a particular set of conditions.
  • the Tm is the temperature at which 50% of the target sequence hybridizes to a perfectly matched probe. See Sambrook et al., supra, page 9.51, hereby incorporated by reference.
  • Tm 81.5°C + 16.6 (loglO[Na+]) + 0.41 (fraction G + C) - 0.63 (% formamide) - (600/1) where 1 is the length of the hybrid in base pairs.
  • Tm 79.8°C + 18.5 (logl0[Na+]) + 0.58 (fraction G + C) + 11.8 (fraction G + C)2 - 0.35 (% formamide) - (820/1).
  • Tm 79.8°C + 18.5 (logl0[Na+]) + 0.58 (fraction G + C) + 11.8 (fraction G + C)2 - 0.35 (% formamide) - (820/1).
  • Tm 79.8°C + 18.5 (logl0[Na+]) + 0.58 (fraction G + C) + 11.8 (fraction G + C)2 - 0.35 (% formamide) - (820/1).
  • the Tm for a particular RNA-DNA hybrid can be estimated by the formula:
  • Tm 79.8°C + 18.5(logl0[Na+j) + 0.58 (fraction G + C) + 11.8 (fraction G + C)2 - 0.50 (% formamide) - (820/1).
  • the Tm decreases by 1-1.5 °C for each 1% of mismatch between two nucleic acid sequences.
  • one having ordinary skill in the art can alter hybridization and/or washing conditions to obtain sequences that have higher or lower degrees of sequence identity to the target nucleic acid. For instance, to obtain hybridizing nucleic acids that contain up to 10% mismatch from the target nucleic acid sequence, 10-15°C would be subtracted from the calculated Tm of a perfectly matched hybrid, and then the hybridization and washing temperatures adjusted accordingly.
  • Probe sequences may also hybridize specifically to duplex DNA under certain conditions to form triplex or other higher order DNA complexes. The preparation of such probes and suitable hybridization conditions are well known in the art.
  • stringent hybridization conditions for hybridization of complementary nucleic acid sequences having more than 100 complementary residues on a filter in a Southern or Northern blot or for screening a library is 50% formamide/6X SSC at 42°C for at least ten hours.
  • Hybridization buffers may also include blocking agents to lower background. These agents are well-known in the art. See Sambrook et al, supra, pages 8.46 and 9.46-9.58, herein incorporated by reference.
  • wash conditions can also be altered to change stringency conditions.
  • a stringent wash condition for duplex DNA of more than 100 base pairs is a 0.2x SSC wash at 65°C for 15 minutes (see Sambrook et al., supra, for SSC buffer).
  • the high stringency wash is preferably preceded by a low stringency wash for such a duplex (4x SSC at 40°C for 15 minutes) to remove excess probe.
  • signal-to-noise ratio of 2x or higher than that observed for an unrelated probe in the particular hybridization assay indicates detection of a specific hybridization.
  • nucleic acids that do not hybridize to each other under stringent conditions are still substantially homologous to one another if they encode polypeptides that are substantially identical to each other. This occurs, for example, when a nucleic acid is created synthetically or recombinantly using a high codon degeneracy as permitted by the redundancy of the genetic code.
  • the arginase encoding polynucleotides of this invention may include both sense and antisense strands of RNA, cDNA, genomic DNA, and synthetic forms and mixed polymers of the above. They may be modified chemically or biochemically or may contain non-natural or derivatized nucleotide bases, as will be readily appreciated by those of skill in the art.
  • Such modifications include, for example, labels (e.g., fluorescent, photometric, radioactive or immunological tags), methylation, phosphorylation, biotinylation, substitution of one or more of the naturally occurring nucleotides with an analog, internucleotide modifications such as uncharged linkages (e.g., methyl phosphonates, phosphotriesters, phosphoramidates, carbamates, etc.), charged linkages (e.g., phosphorothioates, phosphorodithioates, etc.), pendent moieties (e.g., polypeptides), intercalators (e.g., acridine, psoralen, etc.), chelators, alkylators, and modified linkages (e.g., alpha anomeric nucleic acids, etc.)
  • synthetic molecules that mimic polynucleotides in their ability to bind to a designated sequence via hydrogen bonding and other chemical interactions. Such molecules are known in the art and include, for example, those in
  • mutated when applied to nucleic acid sequences means that nucleotides in a nucleic acid sequence may be inserted, deleted or changed compared to a reference nucleic acid sequence. A single alteration may be made at a locus (a point mutation) or multiple nucleotides may be inserted, deleted or changed at a single locus. In addition, one or more alterations may be made at any number of loci within a nucleic acid sequence.
  • the nucleic acid sequence is the wild type nucleic acid sequence for arginase.
  • the nucleic acid sequence may be mutated by any method known in the art.
  • “Operatively linked” expression control sequences refers to a linkage in which the expression control sequence is contiguous with the gene of interest to control the gene of interest, as well as expression control sequences that act in trans or at a distance to control the gene of interest.
  • expression control sequence refers to polynucleotide sequences which are necessary to affect transcription into RNA, and, where appropriate, the expression of protein coding sequences, from polynucleotide sequences to which the expression control sequences are operatively linked.
  • Expression control sequences are sequences which control the transcription, post- transcriptional events and translation of nucleic acid sequences.
  • Expression control sequences include appropriate transcription initiation, termination, promoter and enhancer sequences; efficient RNA processing signals such as splicing and polyadenylation signals; sequences that stabilize cytoplasmic mRNA; sequences that enhance translation efficiency (e.g., ribosome binding sites); sequences that enhance protein stability; and when desired, sequences that enhance protein secretion.
  • control sequences differs depending upon the host organism; in prokaryotes, such control sequences generally include promoter, ribosomal binding site, and transcription termination sequence.
  • control sequences is intended to include, at a minimum, all components whose presence is essential for expression, and can also include additional components whose presence is advantageous, for example, leader sequences and fusion partner sequences.
  • vector is intended to refer to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked.
  • plasmid refers to a circular double stranded DNA loop into which additional DNA segments may be ligated.
  • Other vectors include cosmids, bacterial artificial chromosomes (BAC) and yeast artificial chromosomes (YAC).
  • BAC bacterial artificial chromosome
  • YAC yeast artificial chromosome
  • viral vector Another type of vector, wherein additional DNA segments may be ligated into the genome of a virus that infects a particular host cell of interest. Many viral vectors have been developed for gene transfer into mammalian cells.
  • viral genome has been modified to delete viral genes that are not essential for infection or subsequent replication of the virus and expression of genes in an appropriate host cell.
  • Some host cells have been engineered to express gene products necessary for viral vector replication and expression.
  • Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication). Other vectors can be integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome.
  • certain vectors are capable of directing the expression of genes to which they are operatively linked. Such vectors are referred to herein as "recombinant expression vectors" (or simply, "expression vectors").
  • recombinant host cell (or simply “host cell”), as used herein, is intended to refer to a cell into which a recombinant expression vector has been introduced. Lt should be understood that such terms are intended to refer not only to the particular subject cell but to the progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term “host cell” as used herein.
  • polypeptide encompasses both naturally-occurring and non- naturally-occurring proteins and polypeptides, polypeptide fragments, fusions, mutants, derivatives and analogs. A polypeptide may be monomeric or polymeric.
  • polypeptide fragment refers to a polypeptide that has an amino-terminal and/or carboxy-terminal deletion compared to a full-length polypeptide.
  • the polypeptide fragment is a contiguous sequence in which the amino acid sequence of the fragment is identical to the corresponding positions in the naturally-occurring sequence. Fragments typically are at least 5, 6, 7, 8, 9 or 10 amino acids long, preferably at least 12, 14, 16 or 18 amino acids long, more preferably at least 20 amino acids long, more preferably at least 25, 30, 35, 40 or 45, amino acids, even more preferably at least 50 or 60 amino acids long, and even more preferably at least 70 amino acids long.
  • a “derivative” refers to polypeptides or fragments thereof that are substantially homologous in primary structural sequence but which include, e.g., in vivo or in vitro chemical and biochemical modifications or which incorporate amino acids that are not found in the native polypeptide. Such modifications include, for example, acetylation, carboxylation, phosphorylation, glycosylation, ubiquitination, labeling, e.g., with radionuclides, fluorescent moieties or biotin, and various enzymatic modifications, as will be readily appreciated by those well skilled in the art.
  • a variety of methods for labeling polypeptides and of substituents or labels useful for such purposes are well known in the art, and include radioactive isotopes such as 1251, 32P, 35S, and 3H, ligands which bind to labeled antiligands (e.g., antibodies), fluorophores, chemiluminescent agents, enzymes, and antiligands which can serve as specific binding pair members for a labeled ligand.
  • the choice of label depends on the sensitivity required, ease of conjugation with the primer, stability requirements, and available instrumentation.
  • Methods for labeling polypeptides are well known in the art. See, e..g, Ausubel et al., 1992, hereby incorporated by reference.
  • fusion protein refers to polypeptides comprising polypeptides or fragments coupled to heterologous amino acid sequences. Fusion proteins are useful because they can be constructed to contain two or more desired functional elements from two or more different proteins.
  • a fusion protein comprises at least 10 contiguous amino acids from a polypeptide of interest, more preferably at least 20 or 30 amino acids, even more preferably at least 40, 50 or 60 amino acids, yet more preferably at least 75, 100 or 125 amino acids.
  • Fusion proteins can be produced recombinantly by constructing a nucleic acid sequence which encodes the polypeptide or a fragment thereof in frame with a nucleic acid sequence encoding a different protein or peptide and then expressing the fusion protein.
  • a fusion protein can be produced chemically by crosslinking the polypeptide or a fragment thereof to another protein.
  • analog refers to both polypeptide analogs and non-peptide analogs.
  • polypeptide analog refers to a polypeptide that is comprised of a segment of at least 25 amino acids that has substantial identity to a portion of an amino acid sequence and that has enzyme activity. Typically, polypeptide analogs comprise a conservative amino acid substitution (or insertion or deletion) with respect to the naturally-occurring sequence. Analogs typically are at least 20 amino acids long, preferably at least 50 amino acids long or longer, and can often be as long as a full-length naturally-occurring polypeptide.
  • non-peptide analog refers to a compound with properties that are analogous to those of a reference polypeptide.
  • a non-peptide compound may also be termed a "peptide mimetic” or a "peptidomimetic.” See, e.g., Fauchere, I Adv. Drug Res. 15:29 (1986); Veber and Freidinger, TLNS p.392 (1985); and Evans et al, J. Med. Chem. 30:1229 (1987), which are incorporated herein by reference. Such compounds are often developed with the aid of computerized molecular modeling. Peptide mimetics that are structurally similar to useful peptides may be used to produce an equivalent effect.
  • a paradigm polypeptide i.e., a polypeptide that has a desired biochemical property or pharmacological activity
  • Systematic substitution of one or more amino acids of a consensus sequence with a D-amino acid of the same type may also be used to generate more stable peptides.
  • constrained peptides comprising a consensus sequence or a substantially identical consensus sequence variation may be generated by methods known in the art (Rizo and Gierasch, Ann. Rev. Biochem.. 61:387 (1992), incorporated herein by reference); for example, by adding internal cysteine residues capable of forming intramolecular disulfide bridges which cyclize the peptide.
  • a "polypeptide mutant” or “mutein” refers to a polypeptide whose sequence contains substitutions, insertions or deletions of one or more amino acids compared to the amino acid sequence of a native or wild type protein.
  • a mutein may have one or more amino acid point substitutions, in which a single amino acid at a position has been changed to another amino acid, one or more insertions and/or deletions, in which one or more amino acids are inserted or deleted, respectively, in the sequence of the naturally-occurring protein, and/or truncations of the amino acid sequence at either or both the amino or carboxy termini. Further, a mutein may have the same or different biological activity as the naturally-occurring protein.
  • a mutein may have an increased or decreased biological activity.
  • a mutein has the same or increased arginase activity as a naturally-occurring arginase.
  • a mutein has at least 50% sequence homology to the wild type protein, preferred is 60% sequence homology, more preferred is 70% sequence homology. Even more preferred are muteins having 80%, 85% or 90% sequence homology to the wild type protein. In an even more preferred embodiment, a mutein exhibits 95% sequence identity, even more preferably 97%, even more preferably 98% and even more preferably 99%. Sequence homology may be measured by any common sequence analysis algorithm, such as Gap or Bestfit.
  • Preferred amino acid substitutions are those which: (1) reduce susceptibility to proteolysis, (2) reduce susceptibility to oxidation, (3) alter binding affinity for forming protein complexes, (4) alter binding affinity or enzymatic activity, and (5) confer or modify other physicochemical or functional properties of such analogs.
  • Analogs can include various muteins of a sequence other than the naturally-occurring peptide sequence. For example, single or multiple amino acid substitutions (preferably conservative amino acid substitutions) may be made in the naturally-occurring sequence (preferably in the portion of the polypeptide outside the domain(s) forming intermolecular contacts.
  • a conservative amino acid substitution should not substantially change the structural characteristics of the parent sequence (e.g., a replacement amino acid should not tend to break a helix that occurs in the parent sequence, or disrupt other types of secondary structure that characterizes the parent sequence).
  • Examples of art-recognized polypeptide secondary and tertiary structures are described in Proteins, Structures and Molecular Principles (Creighton, Ed., W. H. Freeman and Company, New York (1984)); Introduction to Protein Structure (C. Branden and J. Tooze, eds., Garland Publishing, New York, N.Y. (1991)); and Thornton et at. Nature 354:105 (1991), which are each incorporated herein by reference.
  • a protein has "homology” or is “homologous” to a protein from another organism if the encoded amino acid sequence of the protein has a similar sequence to the encoded amino acid sequence of a protein of a different organism.
  • a protein may have homology or be homologous to another protein if the two proteins have similar amino acid sequences.
  • two proteins are said to be “homologous,” this does not imply that there is necessarily an evolutionary relationship between the proteins. Instead, the term “homologous” is defined to mean that the two proteins have similar amino acid sequences.
  • a homologous protein is one that exhibits at least 55% sequence identity to the naturally occurring reference protein, preferred is 60% sequence identity, more preferred is 70% sequence identity.
  • homologous proteins that exhibit 80%, 85% or 90% sequence identity to the reference protein. Ln a yet more preferred embodiment, a homologous protein exhibits 95%, 97%, 98% or 99% sequence identity.
  • homologous protein does not imply that the proteins must be functionally similar to each other.
  • a conservative amino acid substitution is one in which an amino acid residue is substituted by another amino acid residue having a side chain ® group) with similar chemical properties (e.g., charge or hydrophobicity).
  • a conservative amino acid substitution will not substantially change the functional properties of a protein.
  • the percent sequence identity or degree of homology may be adjusted upwards to correct for the conservative nature of the substitution. Means for making this adjustment are well known to those of skill in the art (see, e.g., Pearson et al.,1994, herein incorporated by reference).
  • I Isoleucine
  • Leucine L
  • Methionine M
  • Alanine A
  • Valine V
  • Phenylalanine F
  • Tyrosine Y
  • Tryptophan W
  • Sequence homology for polypeptides is typically measured using sequence analysis software.
  • sequence analysis software See, e.g., the Sequence Analysis Software Package of the Genetics Computer Group (GCG), University of Wisconsin Biotechnology Center, 910 University Avenue, Madison, Wisconsin 53705. Protein analysis software matches similar sequences using measure of homology assigned to various substitutions, deletions and other modifications, including conservative amino acid substitutions.
  • GCG contains programs such as "BLASTP", “Gap” and “Bestfit” which can be used with default parameters to determine sequence homology or sequence identity between closely related polypeptides, such as homologous polypeptides from different species of organisms or between a wild type protein and a mutein thereof. See, e.g., GCG Version 6.1.
  • polypeptide sequences compared for homology will generally be at least about 16 amino acid residues, usually at least about 20 residues, more usually at least about 24 residues, typically at least about 28 residues, and preferably more than about 35 residues.
  • database searching using amino acid sequences can be measured by algorithms such as BLASTP known in the art.
  • polypeptide sequences are preferably compared using FASTA with its default parameters (a word size of 2 and the PAM250 scoring matrix), as provided in GCG Version 6.1, herein incorporated by reference.
  • FASTA provides alignments and percent sequence identity of the regions of the best overlap between the query and search sequences (Pearson, 1990, herein incorporated by reference).
  • neurotrophin refers to a trophic factor that helps a neuron survive or grow.
  • a neurotrophin elevates cyclic AMP (cAMP) levels in a neuron.
  • patient includes human and veterinary subjects.
  • putrescine-derived polyamine refers to a polyamine made in a cell from a putrescine molecule or a molecule that was derived from a putrescine molecule.
  • the putrescine molecule can be one that is made in the host cell or one that is transported into the host cell.
  • a "trophic factor” is a substance that helps a cell survive or grow and which elevates cyclic AMP (cAMP) levels.
  • a non-hydrolyzable cyclic AMP (cAMP) analog is a cAMP having a phosphodiesterase-resistant linkage and which therefore has greater bioactivity than an unmodified cAMP molecule.
  • Examples include dibutyryl cAMP (dbcAMP) (Posteraak and Weimann, Methods EnzvmoL. 38, pp. 399-409 (1974); incorporated herein by reference); and Sp-cAMP (Dostmann et al., J. Biol. Chem.. 265, pp. 10484-491 (1990); incorporated herein by reference).
  • Cyclic AMP-Lnduced Axonal Growth on MAG or Mvelin Ls Transcription Dependent To determine whether the cAMP-induced relief of axonal outgrowth inhibition by MAG or myelin depends on transcription, we added a transcriptional inhibitor (5,6-dichloro-l-b-D-ribofuranosylbenzimidazole or "DRB") to neuronal cultures in which cAMP levels had been increased (see Example 1). As shown in Figure 2, elevating cAMP levels in neurons, either by (A) adding dibutyryl (db) cAMP directly to neurons growing on MAG-expressing or control cells; or (B) by priming with neurotrophms (BDNF), blocks inhibition of neuronal growth by MAG.
  • DRB dibutyryl
  • BDNF neurotrophms
  • Arginase is Up-Regulated When cAMP Levels Are Elevated
  • Arginase is a cytosolic enzyme which converts arginine to ornithine and urea.
  • a rate limiting step in polyamine synthesis is the subsequent conversion of ornithine to putrescine and CO 2 by ornithine decarboxylase (ODC).
  • Putrescine can then be converted to other polyamines ("putrescine-derived polyamines") (Fig. 1; see also Slotkin and Bartolome, 1986).
  • cerebellar neurons were primed with neurotrophins (BDNF) or dbcAMP (Example 1), and RNA and protein was extracted from primed neurons (Example 2).
  • BDNF neurotrophins
  • Example 1 RNA and protein was extracted from primed neurons (Example 2).
  • the extracted RNA was used as a template for reverse transcription and PCR amplification using primers specific for the gene encoding the enzyme arginase L ("Arg I"), an isoform of arginase abundant in liver tissue but barely detectable in other tissues.
  • the results of the amplification are shown in Figure 4.
  • lane 1 there are significant levels of Arg I RNA detected in liver, a positive control. There is also detectable Arg I RNA in cerebellar neurons (lane 2). Levels of Arg I RNA increased after exposure of the neurons to either BDNF (lane 3) or dbcAMP (lane 4).
  • Fig 4(b) shows by quantitative PCR that there was about 2-fold less Arg I RNA in untreated cerebellar neurons as in liver.
  • arginase I (Argl) protein is barely detectable in cerebellar neurons (arrows).
  • the amount of Argl proteins increased at least two-fold. This increase peaked around 3 hours post-treatment, and was sustained for 21 hours.
  • the levels of Argl proteins began to decline.
  • arginase J in neurons customarily migrates as a doublet when analyzed by SDS PAGE.
  • the doublet likely reflects a post-translational modification of the native arginase I (e.g., a deletion of one or more amino acids and/or addition of chemical modifications such as
  • Brain- derived neurotrophic factor belongs to the Trk-family of neurotrophins, which includes nerve growth factor (NGF), neurotrophin-3 (NT-3) and neurotrophin 4/5
  • Trk-family neurotrophins act through their signaling Trk tyrosine kinase receptors (TrkA, TrkB, and TrkC) and, in addition, they share a common low affinity receptor, p75. Besides their well-established actions in regulating cell survival, differentiation and proliferation, these Trk-family neurotrophins are involved in processes of neuronal plasticity ((Jelsma and Aguayo, Curr. Opin. NeurobioL. 4, pp. 25 717-725 (1994); Thoenen, Science. 270, pp. 593-598 (1995); each of which is incorporated herein by reference).
  • GDNF glial cell line-derived neurotrophic factor
  • GDNF peripheral nervous system
  • GDNF-like family in addition to GDNF, neurturin (NRTN), arternin (ARTN) and perseph n (PSP) are also identified.
  • NRTN neurturin
  • ARTN arternin
  • PSP perseph n
  • This family of neurotrophins acts through a multicomponent receptor system, distinct from Trk receptors, comprising a high- affinity ligand-binding co-receptor GFR (GDNF family receptor component) and the Ret tyrosine kinase (Baloh et al., Curr. Qpin. Neurobiol.. 10, pp. 103-110 (2000); incorporated herein by reference).
  • Cerebellar neurons were untreated (-) or exposed to 200 ng/ml GDNF for lh, 3h or 5h and the cells lysed in the presence of protease inhibitors.
  • Total protein 23 ⁇ g was subjected to SDS-polyacrylamide gel (12%) electrophoresis (SDS- PAGE), transferred to nitrocellulose membrane and immunostained with antibody to Arg I.
  • SDS-PAGE SDS-polyacrylamide gel
  • ODC ornithine decarboxylase
  • DFMO DL- a-difluoromethyl-ornithine hydrochloride
  • Priming neurons with putrescine in a concentration range of between lO ⁇ M and 25 ⁇ M is sufficient to block the inhibitory effect of (A) MAG and (B) myelin on axonal outgrowth.
  • the blocking effect of putrescine on MAG saturates at doses higher than 25 ⁇ M.
  • priming neurons with putrescine at lO ⁇ M results in at least a two-fold increase in axonal outgrowth, which is similar to the growth from neurons primed with 200 ng/ml BDNF.
  • Priming with putrescine at concentrations between about lO ⁇ M and 50 ⁇ M increase axonal growth on myelin even more dramatically.
  • cerebellar neurons were grown on MAG-expressing CHO cells or a CNS myelin substrate with different concentrations of putrescine. We found that the addition of putrescine without priming only partially blocks the inhibition of axonal growth by MAG or myelin. In the concentration range of between 15 ⁇ M and lOO ⁇ M, the blocking effect of putrescine on the inhibition by MAG or myelin reaches a plateau at about 64% reversal.
  • Axons of the CNS usually do not regenerate when cut in vivo.
  • a peripheral and a central branch such as dorsal root ganglion (DRG) neurons
  • DRG dorsal root ganglion
  • the peripheral branch is cut 1 day or 1 week before the central axons are cut, there is considerable regeneration of these CNS axons (Neumann, S. and Woolf, C.J., Neuron. 23, pp. 83-91 (1999); Richardson, P.M. and Issa, V.M.K., Nature. 309, 791-793 (1984); and Richardson, P.M., et al., Nature. 284, pp. 264-265 (1980); each of which is incorporated herein by reference). If the CNS axons of the DRG neuron are cut without a prior conditioning lesion to the peripheral branch, there is no regeneration.
  • Up-Regulation of Arginase Blocks the Inhibition of Neurite Outgrowth bv MAG
  • arginase I cDNA To determine whether the up-regulation of arginase is sufficient to overcome inhibition of axonal growth by MAG, we introduced an arginase I cDNA into neurons. To achieve nearly 100% transfection efficiency in post-mitotic cells, several groups have used viral vectors to deliver heterologous proteins into neurons and glia with high efficiency and low toxicity (see, e.g., Ghadge et al., J. Neurosci.. 17, pp. 1397-1405 and pp. 8756-66 (1997) incorporated herein by reference). To overexpress arginase in a neuron, we used adenoviral-mediated gene transfer techniques.
  • Adenovirus (Adv) systems have been used extensively to express human as well as non-human proteins. They can be used to infect a broad range of mammalian cells and therefore permit the expression of recombinant proteins in most mammalian cell lines and tissues. They have advantages over retroviruses in that they can infect post-mitotic cells whereas retroviruses cannot.
  • FIG. 11 A shows a neuron that is positively immunostained for GFP and GAP43.
  • Figure 11B shows cerebellar neuron proteins separated by SDS-PAGE and immunoblotted with Argl antibodies (Western blot analysis) (Example 4).
  • Argl see arrow
  • the endogenous levels of Argl are undetectable in 5 ⁇ g protein from GFP-adenovirus infected neurons. Arg I was first detected upon loading 23 ⁇ g total protein from these control cells.
  • DRG neurons have been shown to switch their axonal regenerative response to MAG and myelin from promotion to inhibition during developmenet. The transition occurs sharply between postnatal days 3-4 (DeBellard et al, Mol. Cell. Neurosci.. 7, pp. 89-101 (1996)).
  • MAG axonal regenerative response to MAG
  • PO/1 DRG neurons were isolated and cultured on MAG-expressing CHO cells in the presence of the irreversible ODC inhibitor DFMO (see supra).
  • promotion of PO-1 DRG neurons by MAG is completely abolished (and even slightly reversed) by adding the ODC inhibitor DFMO - axonal growth in the PO-1 DRG neurons is slightly inhibited rather than promoted by MAG.
  • the DFMO effect is MAG-dependent because DFMO alone has no effect on neurite growth on control CHO cells.
  • blocking a step downstream from arginase in the polyamine biosynthetic pathway can switch the neuronal response to MAG from promotion to inhibition.
  • MAG In young neurons, endogenous cAMP and Argl levels are high and axonal growth from these neurons is promoted by MAG. During neuronal development, there is a decrease in the Argl expression levels which coincides with decreases in endogenous cAMP levels. Subsequent to this developmental switch, axonal growth from neurons is inhibited rather than promoted by MAG. Therefore, by changing the cAMP or Argl expression levels in neurons, the developmental switch of neuronal responses to MAG may be modulated. The level and direction of desired modulation of polyamine levels or of arginase activity will thus depend on the cell type and the developmental stage of the targeted neuron.
  • arginase also plays an important role in anti-apoptotic and other neuronal cell death mechanisms and is likely to be involved in neurodegenerative diseases such as amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, and the like (infra). It follows that modulation of neuronal polyamine levels by altering putrescine or arginase activity will be therapeutic in these diseases as well as in the treatment of spinal cord injury and other nervous tissue damage.
  • putrescine As shown above, addition of putrescine to adult neurons can relieve inhibition by myelin (and MAG) of neuronal growth. Putrescine, and putrescine analogs and derivatives which, for example, have longer half-lives, greater bioavailability, and the like, will therefore be useful in compositions and therapeutic methods according to the present invention.
  • the invention thus provides compositions and methods for increasing endogenous putrescine (and derivative polyamine) levels in the cells of the nervous system.
  • Putrescine may be administered directly to the cerebrospinal fluid (CSF) by, for example, by epidural or intrathecal pump or lumbar puncture.
  • CSF cerebrospinal fluid
  • neural or glial cells of the nervous system may be engineered to express altered (e.g., higher) levels of putrescine and other derivative polyamines.
  • the enzyme ornithine amino transferase 0 converts ornithine into pyrroline-5-carboxylate.
  • Inhibitors of OAT such as 5- fluoro-methylornithine, would be expected to increase the levels of ornithine available for polyamine synthesis. (J. Mol. Biol.. 285, pp. 297-309 (1999)).
  • OAT inhibitors would thus constitute a putrescine or derivative polyamine modulatory agent useful for practicing the present invention.
  • another method modulating putrescine and derivative polyamine levels in a neuron is by modulating arginase activity in the cell according to the methods of the invention (see below).
  • Such methods comprise the step of administering a composition according to the invention comprising an arginase modulatory agent.
  • Such methods optionally further comprise the step of monitoring 0 the growth of at least one neuron following administration of a compound of the invention.
  • arginase I and II cDNAs Human, rat and mouse arginase I and II cDNAs have been isolated and characterized (see below).
  • Mammalian arginase I and II polypeptides are approximately 70% identical at the amino acid sequence level and differ primarily in that arginase II has a mitochondrial protein targeting sequence.
  • polypeptide muteins, fragments, analogs, fusions, derivatives and the like which comprise conserved amino acid residues 98-107, 122-131 and 137-146 of arginase at those or different positions (or conservative substitutions of the non-histidine residues within those conserved regions such that at least 70% amino acid sequence identity remains) will retain arginase activity and will be useful in the compositions and methods of the present invention.
  • the present invention thus provides polynucleotides, including single- and double-stranded DNA and RNA (sense or antisense) which are capable of modulating arginase activity in a neuron.
  • the nucleic acid sequences may be used directly to modulate arginase activity in the nervous system, e.g., by expression of a polypeptide having arginase activity, or by expression of an antisense nucleic acid that inhibits arginase activity, in a neuron or glial cell.
  • arginase nucleic acid sequences that encode a polypeptide comprising the conserved amino acid residues 98- 107, 122-131 and 137-146 of human or mammalian arginase I are used.
  • the cDNAs encoding the known mammalian arginase enzymes are approximately 50% identical at the nucleic acid level. Expression of any one of these arginase nucleic acids in a neuron, or in a cell which can provide subsequent arginase activity to a neuron, is thus expected to be useful for modulating arginase activity according to the present invention. Likewise, it is expected that nucleic acid sequences related by at least 50% sequence identity to those, sequences, especially those which comprise sequences that encode the conserved amino acid residues of arginase as discussed above, will be useful in practicing the present invention.
  • Nucleic acid sequences may be expressed by operatively linking them to an expression control sequence in an appropriate expression vector and employing that expression vector to transform an appropriate unicellular host.
  • Expression control sequences are sequences which control the transcription, post-transcriptional events and translation of nucleic acid sequences.
  • Such operative linking of a nucleic sequence of this invention to an expression control sequence includes, if not already part of the nucleic acid sequence, the provision of a translation initiation codon, ATG or GTG, in the correct reading frame upstream of the nucleic acid sequence.
  • Useful expression vectors for example, may consist of segments of chromosomal, non- chromosomal and synthetic nucleic acid sequences.
  • host/expression vector combinations may be employed in expressing the polynucleotide sequences which act as arginase modulatory agents of the invention.
  • Such host/expression vector combinations are well-known in the art and may be selected, for example, based on the host cell type chosen as a target for gene delivery.
  • the host cell will be a mammalian host cell.
  • the host cell may be engineered to constitutively express the arginase modulatory agent of the invention.
  • the host cell may be engineered to express the arginase modulatory agent in a regulated fashion, e.g., upon receiving a molecular signal such as the presence or absence of a regulatory molecule required for activation by expression control sequences.
  • the host cell may be one that is grown in culture and then introduced into a subject or patient in need of treatment, Alternatively, the host cell may be one that resides in or is otherwise in communication with a part of the nervous system of the subject or patient in need of treatment.
  • Ln preferred embodiments, eukaryotic cells, and more preferably, mammalian cells may be used as host cells.
  • Expression in mammalian cells can be achieved using a variety of plasmids, including pSV2, pBC12BL, and p91023, as well as lytic virus vectors (e.g., vaccinia virus, adenovirus, AAV and baculovims), episomal virus vectors (e.g., bovine papillomavirus), and retroviral vectors (e.g., murine retroviruses and HIV), including lentivectors (see, e.g., Consiglio et al., Nature Med.. 7, pp. 310-316 (2001), incorporated herein by reference).
  • Useful vectors for insect cells include baculoviral vectors and pVL 941. These and other viral and non- viral vectors are well-known to those of skill in the art of nucleic acid delivery and expression in eukaryotic cells.
  • any of a wide variety of expression control sequences may be used in these vectors to express the polynucleotide sequences of this invention.
  • Such useful expression control sequences include the expression control sequences associated with structural genes of the foregoing expression vectors.
  • Expression control sequences that control transcription include, e.g., promoters, enhancers and transcription termination sites.
  • Expression control sequences in eukaryotic cells that control post-transcriptional events include splice donor and acceptor sites and sequences that modify the half-life of the transcribed RNA, e.g., sequences that direct poly(A) addition or binding sites for RNA-binding proteins.
  • Expression control sequences that control translation include ribosome binding sites, sequences which direct targeted expression of the polypeptide to or within particular cellular compartments, and sequences in the 5' and 3' untranslated regions that modify the rate or efficiency of translation.
  • Expression control sequences may also include sequences that target a nucleic acid or protein to a particular sub-cellular location or compartment, e.g., mitochondrial target sequences, nuclear localization sequences, cytoplasmic retention sequences, and secretion sequences which target a protein to the endoplasmic reticulum and thus the secretion pathway of the host cell.
  • mitochondrial target sequences e.g., mitochondrial target sequences, nuclear localization sequences, cytoplasmic retention sequences, and secretion sequences which target a protein to the endoplasmic reticulum and thus the secretion pathway of the host cell.
  • secretion sequences which target a protein to the endoplasmic reticulum and thus the secretion pathway of the host cell.
  • useful expression control sequences include, for example, the early and late promoters of SV40 or adenovirus, splicing sequences of SV40, the CMV promoter/enhancer, the T3 and T7 promoters, the promoter for 3- phosphoglycerate kinase or other glycolytic enzymes, the promoters of acid phosphatase, e.g., Pho5, the promoters of the yeast ⁇ -mating system, the GALl or GAL 10 promoters, and other constitutive and inducible promoter sequences known to control the expression of genes of prokaryotic or eukaryotic cells or their viruses, and various combinations thereof appropriately modified to act in the selected host cell.
  • the early and late promoters of SV40 or adenovirus splicing sequences of SV40, the CMV promoter/enhancer, the T3 and T7 promoters, the promoter for 3- phosphoglycerate kinase or other glycolytic enzymes
  • Promoters that may be induced in the brain include but are not limited to those described in Chen et al., Mol. Pharmacol.. 54, pp. 495-503 (1998); and Tremblay et al., Proc. Natl. Acad. Sci. U.S.A. 95, pp.12580-12585(1998); each of which is incorporated herein by reference. Those of skill in the art will immediately appreciate how to identify and use other expression control sequences that may be used to achieve regulated gene expression in cells of the brain and nervous system.
  • nucleic acid vectors also include a selectable or amplifiable marker gene and means for selecting or amplifying the copy number of the gene of interest.
  • marker genes are well-known in the art.
  • Nucleic acid vectors may also comprise stabilizing sequences (e.g., ori- or ARS-like sequences and telomere-like sequences), or may alternatively be designed to favor directed or non-directed integration into the host cell genome.
  • nucleic acid sequences of this invention are inserted in frame into an expression vector that allows high level expression of an RNA which encodes a protein comprising the encoded nucleic acid sequence of interest.
  • nucleic acid cloning and sequencing methods are well known to those of skill in the art and are described in an assortment of laboratory manuals, including Ausubel et al., (supra). Product information from manufacturers of biological, chemical and immunological reagents also provide useful information.
  • not all vectors and expression control sequences will function equally well to express the nucleic acid sequences of this invention. Neither will all hosts function equally well with the same expression system.
  • one of skill in the art may make a selection among these vectors, expression control sequences and hosts without undue experimentation and without departing from the scope of this invention. For example, in selecting a vector, the host must be considered because the vector must be replicated in it.
  • the vector's copy number, the ability to control that copy number, the ability to control integration, if any, and the expression of any other proteins encoded by the vector, such as antibiotic or other selection markers, should also be considered.
  • Transformation and other methods of introducing nucleic acids into a host cell can be accomplished by a variety of methods which are well known in the art (see, for instance, Ausubel, supra).
  • Bacterial, yeast, plant or mammalian cells are transformed or transfected with an expression vector, such as a plasmid, a cosmid, or the like, wherein the expression vector comprises the nucleic acid of interest.
  • the cells may be infected by a viral expression vector comprising the nucleic acid of interest.
  • transient or stable expression of the nucleic acid and an encoded polypeptide will be constitutive or inducible.
  • One having ordinary skill in the art will be able to decide whether to express a polynucleotide or polypeptide transiently or stably, and whether to express an encoded protein constitutively or in a regulated fashion (e.g., inducibly).
  • a wide variety of unicellular host cells are useful in expressing the DNA sequences of this invention.
  • These hosts may include well known eukaryotic and prokaryotic hosts, animal cells such as CHO, BHK, MDCK and various murine cells, e.g., 3T3 and WEHI cells, African green monkey cells such as COS 1, COS 7, BSC 1, BSC 40, and BMT 10, and human cells such as VERO, WI38, and HeLa cells.
  • Useful neural cells include but are not limited to rat hippocampal cell lines such as HI 9-7, HT- 22; human neuroblastoma cells such as SH-SY5Y; and mouse neuroblastoma cells such as N2a and N18.
  • the invention is in no way envisioned to be limited to the particular host cell selected for expression of an arginase modulatory agent. Particular details of gene delivery, gene expression and purification of recombinant proteins are well documented and are understood by those of skill in the art. Further details on the various technical aspects of each of the steps used in recombinant production of foreign genes in heterologous cell expression systems can be found in a number of texts and laboratory manuals in the art. See, e.g., Ausubel et al., supra, and Sambrook et al., supra, and Kieser et al, supra, incorporated herein by reference.
  • Ornithine is a known feedback inhibitor of arginase 1. Lt is thus anticipated that molecules which partially or fully inhibit or compete with the ability of ornithine to feedback inhibit arginase L activity will be useful modulators of arginase function in a neuron. Such arginase modulatory molecules may be easily identified by performing classic enzyme substrate inhibition and competition studies using arginase assays in the presence of the arginase inhibitor ornithine and varying concentrations of one or more test compounds. Such arginase modulatory agents may, but need not necessarily, act in a concentration and time dependent manner.
  • Genetic selections and analyses e.g., looking for mutations that suppress particular phenotypes
  • a model genetic organism such as yeast or fruit fly
  • Genetic selections and analyses may be used as an alternative to or in conjunction with enzymatic assays to identify arginase modulatory agents.
  • N(omega)-hydroxy-l-arginine is another example of an arginase inhibitor (Iniesta et al., J. Exp. Med..193. pp. 777-784 (2001), incorporated herein by reference). See also Khangulov et al., Biochemistry. 37(23), pp. 8539-50 (1998), incorporated herein by reference). Any arginase inhibitor may be used as an arginase modulatory agent, or may be used to identify agents such as small molecules which are capable of relieving arginase inhibition in vivo and which are thereby arginase modulatory agents according to the present invention.
  • the putrescine, derivative polyamine and arginase modulatory agents of this invention may be formulated into pharmaceutical compositions and administered in vivo at an effective dose to treat the particular clinical condition addressed.
  • Administration of one or more of the pharmaceutical compositions according to this invention will be useful for regulating, e.g., for promoting or inhibiting neural growth or regeneration in the nervous system, for treating injuries or damage to nervous tissue or neurons, and for treating neural degeneration associated with injuries (such as traumas) to the nervous system, disorders or diseases, including those associated with apoptosis, necrosis or other forms of cell death.
  • injuries, diseases or disorders include spinal cord injury, brain injury, aneurysms and strokes.
  • Such injuries, diseases or disorders also include PNS injury, viral infection (e.g., by herpes virus or HLV), encephalitis (viral or non-viral), mitochondrial disease, Creutzfeldt- Jacob disease, kuru, multiple system atrophy, multiple sclerosis, peripheral neuropathies and progressive supranuclear palsy.
  • viral infection e.g., by herpes virus or HLV
  • encephalitis viral or non-viral
  • mitochondrial disease e.g., Creutzfeldt- Jacob disease
  • kuru multiple system atrophy
  • multiple sclerosis e.g., peripheral neuropathies and progressive supranuclear palsy.
  • Neurodegenerative diseases include, but are not limited to: amyotropic lateral sclerosis (Lou Gehrig's disease; "ALS”); Parkinson's Disease; Parkinson's Plus Syndromes; ALS-Parkinson dementia complex; Huntington's Disease; Alzheimer's Disease; Pick Disease; Wilson's Disease; hepatolenticular degeneration; environmental toxins, including manganese and carbon monoxide poisoning; inherited epilepsies; nutritional deficiency states (e.g., Wernicke-Korsakoff syndrome, B12 deficiency and pellagra); prolonged hypoglycemia or hypoxia; paraneoplastic syndromes; heavy metal exposure (e.g., arsenic, bismuth, gold, manganese and mercury); dialysis dementia; Schilder disease; lipid-storage diseases; cerebrocerebellar degeneration; dementia with spastic paraplegia; progressive supranuclear palsy; Binswanger Disease; brain tumor or abcess; Marchiava-Bignami Disease
  • Determination of a preferred pharmaceutical formulation and a therapeutically efficient dose regiment for a given application is within the skill of the art taking into consideration, for example, the condition and weight of the patient, the extent of desired treatment and the tolerance of the patient for the treatment. See, e.g., Handbook of Pharmaceutical Additives: An International Guide to More than 6000 Products by Trade Name, Chemical, Function, and Manufacturer, Ashgate Publishing Co., eds., M. Ash and I. Ash, 1996; The Merck Index: An Encyclopedia of Chemicals, Drugs and Biologicals, ed. S. Budavari, annual; Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, POLYAMINE ; Martindale: The Complete Drug Reference, ed. K.
  • Administration of the neuronal polyamine and arginase modulators of the invention may be accomplished using any of the conventionally accepted modes of administration of agents which are used to treat injuries or disorders, especially those relating to the central and peripheral nervous system.
  • compositions of this invention may be in a variety of forms, which may be selected according to the preferred modes of administration. These include, for example, solid, semi-solid and liquid dosage forms such as tablets, capsules, pills, powders, creams, liquid solutions or suspensions, syrups, suppositories, injectable and infusible solutions, aerosols and the like.
  • solid, semi-solid and liquid dosage forms such as tablets, capsules, pills, powders, creams, liquid solutions or suspensions, syrups, suppositories, injectable and infusible solutions, aerosols and the like.
  • the preferred form depends on the intended mode of administration and therapeutic application.
  • Modes of administration may include, but are not limited to, oral, parenteral (including subcutaneous, intravenous, intramuscular, intra-articular, intra-synovial, cisternal, intrathecal, intrahepatic, intralesional and intracranial injection or infusion), topical, rectal, nasal, buccal, vaginal, by inhalation, or by an implanted reservoir, external pump or catheter.
  • the polyamine and arginase modulatory agents of this invention may, for example, be placed into sterile, isotonic formulations with or without cofactors which stimulate uptake or stability.
  • the formulation is preferably liquid, or may be lyophilized powder.
  • an agent of the invention may be diluted with a formulation buffer comprising 5.0 mg/ml citric acid monohydrate, 2.7 mg/ml trisodium citrate, 41 mg/ml mannitol, 1 mg/ml glycine and 1 mg/ml polysorbate 20.
  • This solution can be lyophilized, stored under refrigeration and reconstituted prior to administration with sterile Water-For-lnjection (USP).
  • compositions also will preferably include conventional pharmaceutically acceptable carriers well known in the art (see pharmaceutical references, supra).
  • Such pharmaceutically acceptable carriers may include other medicinal agents, carriers, including genetic carriers, adjuvants, excipients, etc., such as human serum albumin or plasma preparations.
  • the compositions are preferably in the form of a unit dose and will usually be administered one or more times a day.
  • the compositions comprising a compound of this invention will contain from about 0.1 to about 90% by weight of the active compound, and more generally from about 10% to about 30%.
  • the compositions may contain common carriers and excipients, such as corn starch or gelatin, lactose, sucrose, microcrystalline cellulose, kaolin, mannitol, dicalcium phosphate, sodium chloride and alginic acid.
  • the compositions may contain croscarmellose sodium, microcrystalline cellulose, corn starch, sodium starch glycolate and alginic acid.
  • the pharmaceutical compositions are in the form of, for example, a tablet, capsule, suspension or liquid. Solid formulations such as tablets and capsules are particularly useful. Sustained release or enterically coated preparations may also be devised. For pediatric and geriatric applications, suspensions, syrups and chewable tablets are especially suitable.
  • the pharmaceutical composition is preferably made in the form of a dosage unit containing a therapeutically-effective amount of the active ingredient. Examples of such dosage units are tablets and capsules.
  • the tablets and capsules which can contain, in addition to the active ingredient, conventional carriers such as binding agents, for example, acacia gum, gelatin, methylcellulose, sodium carboxymethylcellulose, polyvinylpyrrolidone (Povidone), hydroxypropyl methylcellulose, sucrose, starch and ethylcellulose sorbitol, or tragacanth; fillers, for example, calcium phosphate, glycine, lactose, maize-starch, sorbitol, or sucrose; lubricants, for example, magnesium stearate, or other metallic stearates, stearic acid, polyethylene glycol, silicone fluid, talc, waxes, oils and silica, colloidal silica or talc; disintegrants, for example, potato starch, flavoring or coloring agents, or acceptable wetting agents.
  • binding agents for example, acacia gum, gelatin, methylcellulose, sodium carboxymethylcellulose, polyvinylpyrrolidone (Povidon
  • Oral liquid preparations generally are in the form of aqueous or oily solutions, suspensions, emulsions, syrups or elixirs may contain conventional additives such as suspending agents, emulsifying agents, non-aqueous agents, preservatives, coloring agents and flavoring agents.
  • Oral liquid preparations may comprise lipopeptide micelles or monomeric forms of the lipopeptide.
  • additives for liquid preparations include acacia, almond oil, ethyl alcohol, fractionated coconut oil, gelatin, glucose syrup, glycerin, hydrogenated edible fats, lecithin, methyl cellulose, methyl or propyl para-hydroxybenzoate, propylene glycol, sorbitol, or sorbic acid.
  • Intravenous (LV) use a water soluble form of the polyamine or arginase modulator can be dissolved in any of the commonly used intravenous fluids and administered by infusion.
  • Intravenous formulations may include carriers, excipients or stabilizers including, without limitation, calcium, human serum albumin, citrate, acetate, calcium chloride, carbonate, and other salts.
  • Intravenous fluids include, without limitation, physiological saline or Ringer's solution.
  • Polyamine and arginase modulators, optionally coupled to other carrier molecules, may also be placed in injectors, cannulae, catheters and lines.
  • Formulations for parenteral administration can be in the form of aqueous or non-aqueous isotonic sterile injection solutions or suspensions. These solutions or suspensions can be prepared from sterile powders or granules having one or more of the carriers mentioned for use in the formulations for oral administration.
  • Lipopeptide micelles may be particularly desirable for parenteral administration.
  • the compounds can be dissolved in polyethylene glycol, propylene glycol, ethanol, corn oil, benzyl alcohol, sodium chloride, and/or various buffers.
  • a sterile formulation of a polyamine or arginase modulatory agent, or a suitable soluble salt form of the compound, for example a hydrochloride salt can be dissolved and administered in a pharmaceutical diluent such as Water-for-Injection (WFI), physiological saline or 5% glucose.
  • WFI Water-for-Injection
  • Injectable depot forms may be made by forming microencapsulated matrices of the compound in biodegradable polymers such as polylactide- polyglycolide. Depending upon the ratio of drug to polymer and the nature of the particular polymer employed, the rate of drug release can be controlled. Examples of other biodegradable polymers include poly(orthoesters) and poly(anhydrides). Depot injectable formulations are also prepared by entrapping the drug in microemulsions that are compatible with body tissues.
  • the compounds of the present invention can also be prepared in suitable forms to be applied to the skin, or mucus membranes of the nose and throat, and can take the form of creams, ointments, liquid sprays or inhalants, lozenges, or throat paints.
  • Such topical formulations further can include chemical compounds such as dimethylsulfoxide (DMSO) to facilitate surface penetration of the active ingredient.
  • DMSO dimethylsulfoxide
  • a sterile formulation of a polyamine or arginase modulatory agent or suitable salt forms thereof may be administered in a cream, ointment, spray or other topical dressing.
  • Topical preparations may also be in the form of bandages that have been impregnated with a therapeutic composition.
  • the compounds of the present invention can be presented in liquid or semi-liquid form optionally formulated in hydrophobic or hydrophilic bases as ointments, creams, lotions, paints or powders.
  • the compounds of the present invention can be administered in the form of suppositories admixed with conventional carriers such as cocoa butter, wax or other glyceride.
  • a sterile formulation of the peptide or lipopeptide or salt form of the compound may be used in inhalers, such as metered dose inhalers, and nebulizers.
  • the compounds of the present invention can be in powder form for reconstitution in the appropriate pharmaceutically acceptable carrier at the time of delivery.
  • the unit dosage form of the compound can be a solution of the compound or a salt thereof, in a suitable diluent in sterile, hermetically sealed ampules.
  • concentration of the compound in the unit dosage may vary, e.g. from about 1 percent to about 50 percent, depending on the compound used and its solubility and the dose desired by the physician.
  • each dosage unit preferably contains from 50-500 mg of the active material.
  • the dosage employed preferably ranges from 100 mg to 3 g, per day, depending on the route and frequency of administration.
  • compositions of this invention may also be administered using microspheres, liposomes, other microparticulate delivery systems or controlled or sustained release formulations placed in, near, or otherwise in communication with affected tissues, the bloodstream, the cerebrospinal fluid, or other locations, including muscle, which enable the targeting of the agent to an affected location in the nervous system.
  • the compositions of the invention can be delivered using controlled (e.g., capsules) or sustained release delivery systems (e.g., bioerodable matrices).
  • Exemplary delayed release delivery systems for drug delivery that are suitable for administration of the compositions of the invention are described in U.S. Patent Nos. 4,452,775 (issued to Kent), 5,239,660 (issued to Leonard), 3,854,480 (issued to Zaffaroni).
  • sustained release carriers include semipermeable polymer matrices in the form of shaped articles such as suppositories or microcapsules.
  • Implantable or microcapsular sustained release matrices include polylactides (U.S. Patent No. 3,773,319; EP 58,481), copolymers of L-glutamic acid and gamma ethyl-L- glutamate (Sidman et al, Biopolymers, 22, pp. 547-56 (1985)); poly(2-hydroxyethyl- methacrylate) or ethylene vinyl acetate (Langer et al, J. Biomed. Mater. Res.. 15, pp. 167-277 (1981); Langer, Chem. Tech..
  • Liposomes containing polyamine and arginase modulatory agents can be prepared by well-known methods (See, e.g. DE 3,218,121; Epstein et al., Proc. Natl Acad. Sci. U.S.A. 82, pp. 3688-92 (1985); Hwang et al., Proc. Natl Acad. Sci. U.S.A. 77, pp. 4030-34 (1980); U.S. Patent Nos. 4,485,045 and 4,544,545). Ordinarily the liposomes are of the small (about 200-800 Angstroms) unilamellar type in which the lipid content is greater than about 30 mol.% cholesterol. The proportion of cholesterol is selected to control the optimal rate of agent release.
  • the polyamine and arginase modulatory agents of this invention may also be attached to liposomes, which may optionally contain other agents to aid in targeting or administration of the compositions to the desired treatment site. Attachment of such agents to liposomes may be accomplished by any known cross- linking agent such as heterobifunctional cross-linking agents that have been widely used to couple toxins or chemotherapeutic agents to antibodies for targeted delivery. Conjugation to liposomes can also be accomplished using the carbohydrate-directed cross-linking reagent 4-(4-maleimidophenyl) butyric acid hydrazide (MPBH) (Duzgunes et al., J. Cell Biochem. Abst. Suppl. 16E 77 (1992)). Routes of Administration
  • Cells which have been engineered to express one or more polyamine or arginase modulatory agents of the invention may be used in therapeutic treatment regimes. Such engineered cells may be used to synthesize a therapeutic agent which can then be administered independently to a host. Alternatively, cells transformed, transfected, or infected with exogenous nucleic acid such as DNA or RNA that activates expression of a polyamine or arginase modulatory agent of the invention that is secreted or released from the engineered cell may be used directly as a therapeutic, e.g., by implanting such engineered cells into a host at a region which is in communication with the targeted tissue or cells in need of treatment.
  • exogenous nucleic acid such as DNA or RNA that activates expression of a polyamine or arginase modulatory agent of the invention that is secreted or released from the engineered cell
  • Viral or non-viral gene delivery into cells which then over (or under) express a polyamine or arginase modulatory agent according to the invention may be performed in vitro or in vivo by any of a number of techniques well known to those of skill in the art. A number of such delivery methods have been shown to work with neurons.
  • neuronal cells can be infected with a viral vector which causes the infected host cells to express arginase at high levels.
  • Arginase I which is not normally a secreted protein, can be engineered to possess a signal peptide required for secretion of a protein from a host cell.
  • signal peptides are characterized by their length (about 16-30 amino acids) and hydrophobicity and which are not highly conserved at the amino acid sequence level (see, e.g., Lodish et al, Molecular Cell Biology, 3d ed., Scientific American Books, W.H. Freeman and Company, New York, 1995, Chapter 16).
  • Amino acid residues which function as a signal sequence for secretion in a eukaryotic cell may be engineered onto the N- terminus of a heterologous protein by any of a number of routine genetic engineering methods well known to those of skill in the art. See, e.g., Farrell et al, Proteins. 41, pp.144-53 (2000) (see also http://www. healthtech.com/2001/pex); Borngraber et al., Protein Expr. Purif.. 14, pp. 237-46 (1998); Collins-Racie et al, Biotechnology. 13, pp. 982-987 (1995); U.S. 5,747,662; WO00/50616; WO99/53059; and WO96/27016; each of which is incorporated herein by reference in its entirety.
  • Host cells which express a secreted form of arginase would be expected to elevate arginase levels in the cerebrospinal fluid (CSF) which bathes the nervous system. Such arginase would then convert arginine in the CSF to ornithine which would be taken up by other cells as is arginine, by cationic amino acid transporters. Alternatively, it is possible to provide arginase, e.g., by injection, directly to the CSF. Ornithine would then be available at higher levels for polyamine synthesis through the actions of intracellular ornithine decarboxylase (ODC). Transfected cells, secreting other forms of arginase modulatory agents, may be administered to a site of neuronal injury or degeneration in a similar manner.
  • CSF cerebrospinal fluid
  • ODC intracellular ornithine decarboxylase
  • homologous recombination techniques allow the skilled worker to replace or modify endogenous genes in a mammalian cell -- for activation, inactivation or alteration of gene coding, including intracellular targeting sequences, and non- coding (regulatory) sequences, such as transcription control sequences and other regulatory sequences which control expression levels of selected genes that modulate putrescine, polyamine or arginase activity.
  • non- coding (regulatory) sequences such as transcription control sequences and other regulatory sequences which control expression levels of selected genes that modulate putrescine, polyamine or arginase activity.
  • homologous recombination techniques see, e.g., U.S. 6,214,622 and 6,054,288, which are incorporated herein by reference.
  • polyamine regulatory sequences see, e.g., Veress et al, Biochem.
  • Putrescine, derivative polyamine and arginase modulatory agents of this invention can also be delivered by spinal implantation (e.g., into the cerebrospinal fluid) of cells or other biocompatible materials engineered to release or secrete polyamine and arginase modulatory agents according to this invention.
  • Cell secretion rates or material release rates of the agent are measured in vitro (e.g., in cell culture where applicable) and then extrapolated based on relative volumes, in vivo half-lives, and other parameters understood by those of skill in the art.
  • transfected cells or biocompatible delivery materials that release polyamine and arginase modulatory agents may be encapsulated into immunoisolatory capsules or chambers and implanted into the brain or spinal cord region using available methods that are known to those of skill in the art. See, e.g., U.S. Patent Nos. 6,179,826, 6,083,523; 5,676,943; 5,653,975 and 5,487,739; and WO 89/04655; WO 92/19195; WO93/00127; EP 127,989; all of which are incorporated herein by reference.
  • a pump and catheter-like device may be implanted at or inserted into the site of injury to administer an agent of the invention on a timely basis and at the desired concentration, which can be selected and empirically modified by one of skill in the art.
  • Such pharmaceutical delivery systems are well known to those of skill in the art. See, e.g., U.S. Patent No. 4,578,057 and references cited therein; for implantable pumps, see, e.g., http://www.medtronic.com/); which are each incorporated herein by reference.
  • this invention provides a method for treating a condition, disease or disorder associated with neuronal degeneration or lack of neuronal growth in mammals, including humans and other animals.
  • the term "treating" is used to denote both the prevention of neuronal death and the control of axonal growth, axonal sprouting, and neural progenitor cell proliferation after the host animal has become affected.
  • An established condition, disease or disorder may be one that is acute or chronic.
  • the method comprises administering to the human or other animal an effective dose of a compound of this invention.
  • An effective dose of putrescine for example, is generally between about 10 "6 and about 10 6 ⁇ M/kg putrescine, putrescine-related analogs or derivatives, or pharmaceutically acceptable salts thereof.
  • the putrescine, putrescine-related analogs or derivatives may be administered alone or as part of a combination therapy.
  • a preferred dose is from about 0.5 to about 80 ⁇ M/kg of putrescine, putrescine-related analogs or derivatives, or pharmaceutically acceptable salts thereof.
  • a more preferred dose is from about 1 to 10 ⁇ M/kg putrescine, putrescine-related analogs or derivatives, or a pharmaceutically acceptable salt thereof.
  • These dosages for putrescine may be used as a starting point by one of skill in the art to determine and optimize effective dosages of other putrescine, putrescine-related analogs or derivatives, and arginase modulating agents of the invention.
  • the invention provides a method for treating a condition, disease or disorder associated with neuronal degeneration or lack of neuronal growth in a subject with a therapeutically-effective amount of a putrescine, a putrescine- derived polyamine or arginase modulatory agent of the invention.
  • the phrase "therapeutically-effective amount” means an amount of putrescine, a putrescine-derived polyamine or arginase modulatory agent of the invention, such that the subject shows a detectable improvement in neuronal growth or regeneration after being treated under the selected administration regime (e.g., the selected dosage levels and times of treatment).
  • treating is defined as administering, to a subject, a therapeutically-effective amount of a compound of the invention, to prevent the occurrence of or to control or eliminate symptoms associated with a condition, disease or disorder associated with neuronal death or lack of neuronal growth.
  • subject as described herein, is defined as a mammal or a cell in culture. In a preferred embodiment, a subject is a human or other animal patient in need of treatment.
  • a compound of the invention can be administered alone, or in combination with other compounds (e.g., a "cocktail"), including but not limited to other compounds of the invention.
  • a compound of the invention may be administered as a single daily dose or in multiple doses per day.
  • the treatment regime may require administration over extended periods of time, e.g., for several days or for from two to four weeks.
  • the amount per administered dose or the total amount administered will depend on such factors as the nature and severity of the symptoms, the age and general health of the patient, the tolerance of the patient to the treatment program.
  • the behavior of a neuron in the presence of the specific myelin inhibitor MAG in vitro parallels its behavior in the presence of myelin both in vitro and in vivo. While not intending to be bound by theory, this suggests that similar molecular mechanisms may be used to overcome a variety of neuronal growth inhibitors.
  • the assay systems described herein are thus extremely useful for monitoring the effect of a variety of agents, alone or in combination, on the inhibitory effects of myelin on neuronal growth.
  • Strategies can now be designed to look for agents which relieve inhibition and which allow neurons to grow in the presence of myelin inhibitors in general or MAG in particular.
  • Such an agent (or combination of agents) can then be administered to damaged nerves reversing the inhibitory effects of myelin or MAG in vivo and allowing nerve regeneration to proceed.
  • the inhibitory effects of myelin and MAG were shown to be partially or fully blocked or relieved by agents that increase putrescine and derivative polyamine levels, including agents which increase arginase activity in a neuron.
  • agents that increase putrescine and derivative polyamine levels including agents which increase arginase activity in a neuron.
  • agents that increase putrescine and derivative polyamine levels including agents which increase arginase activity in a neuron.
  • agents which can modulate the activity of putrescine, derivative polyamines or arginase in a neuron may be administered, alone or in combination, to damaged nerves to reverse the inhibitory effects of myelin or MAG in vivo and to allow regeneration to proceed.
  • the properties of MAG as a negative axonal guidance cue may be used to guide regenerating axons to their correct target and keep them on the correct path.
  • putrescine, derivative polyamines, arginase modulatory agents, or modified forms of these or other agents which can alter (e.g., increase) polyamine levels in a neuron may be administered to the precise regions of the regenerating nervous tissue to encourage or contain growth along exact pathways.
  • Agents that increase putrescine and derivative polyamine levels in a neuron, including agents which increase arginase activity, and methods for using compositions comprising such an agent, will thus be useful for regulating neural growth or regeneration in the nervous system and for treating injuries or damage to nervous tissue or neurons.
  • compositions and methods of the invention will also be useful for treating neural degeneration associated with disorders or diseases and for treating a disease, disorder or condition associated with apoptosis, necrosis or other forms of cell death, such as amyotrophic lateral sclerosis, Alzheimer's disease,
  • compositions and methods of the invention will also be useful for treating an injury or neural abnormality associated with spinal cord injury, brain injury, aneurysms and strokes.
  • compositions and methods of the invention will also be useful for treating an injury or neural abnormality associated with PNS injury, viral infection (e.g., by herpes virus or HIV), encephalitis (viral or non-viral), mitochondrial disease, kuru and peripheral neuropathies.
  • agents which increase putrescine and derivative polyamine levels including agents which increase arginase activity in a neuron, will be useful for treating memory and learning defects and disorders associated with neuronal death or lack of neuronal growth.
  • agents which increase arginase activity in a neuron will be useful for treating memory and learning defects and disorders associated with neuronal death or lack of neuronal growth.
  • There are many molecular and morphological similarities between the cAMP-dependent ability of neurotrophins and dbcAMP to overcome inhibition by MAG and myelin and the changes associated with memory and learning (Bach et al, Proc. Natl Acad. Sci. U.S.A. 96, pp. 5280-85 (1999); incorporated herein by reference).
  • the animal model of memory acquisition is termed "long-term potentiation".
  • myelin or MAG inhibitors such as putrescine, derivative polyamines and arginase modulatory agents, or modified forms of these or other agents which can modulate the activity of putrescine, derivative polyamines or arginase in a neuron, either individually or in various combinations, will block the inhibitory effects of myelin, MAG and/or other inhibitory molecules and encourage axonal regeneration to take place.
  • arginase modulatory agents such as TGF ⁇ , LL4, LL10 and PGE2
  • trophic agents such as neurotrophins (including but not limited to BDNF, GDNF, NGF, NT3, NT4, IGF1, CNTF, galanin), EGF, PDGF, bFGF, neuroregulin (also known as aria, GGF or neu), oncostatin M and LLFl)
  • EGF EGF
  • PDGF bFGF
  • neuroregulin also known as aria, GGF or neu
  • Neurons were isolated essentially as described in Doherty et al, Nature. 343, pp. 464-66 (1990); Neuron, 5, pp. 209-19 (1990); and Kleitman et al., Culturing Nerve Cells, pp. 337-78, MIT Press, Cambridge, MA/London, England (G. Banker and K. Goslin, Eds.) (1991). Briefly, for animals up to nine days of age, the cerebellum, from two animals were removed and combined in 5 ml of 0.025% trypsin in PBS, triturated, and incubated for a further 10 minutes (min.) at 37°C.
  • Trypsinization was stopped by addition of 5 ml DMEM containing 10% fetal calf serum (FCS) and cells were centrifuged at 800 rpm for 6 min. The trypsinized cells were resuspended to a single cell suspension in 2 ml of SAT containing 2% FCS (progesterone, 20nM; selenium, 30nM; putrescine, lOO ⁇ M; insulin, 5 ⁇ g/ml; BSA 4 mg/ml; L-thyroxine, O.l ⁇ g/ml; tri-iodo-thyronine, 0.08 ⁇ g/ml) (Doherty et al, 1990).
  • FCS fetal calf serum
  • ganglia were removed from two animals and incubated in 5 ml of Sat medium containing 0.025% trypsin and 0.15% collagenase type I (Worthington) for 30 min. at 37°C. The ganglia were triturated with a fire-polished Pasteur pipette. Trypsinization was stopped by adding 5 ml of DMEM containing 10% FCS, centrifuged at 800 rpm for 6 min., and resuspended in 2 ml of SAT (DeBellard et al., 1996). Cells were counted with a Coulter counter.
  • CHO cells deficient in the dihydrofolate reductase (dhfr) gene (Urlaub and Chasin, Proc. Natl Acad. Sci. U.S.A. 77, pp. 4216- 20 (1980)) were transfected with a MAG-cDNA expression plasmid with the dhfr gene and the L-MAG cDNA, cells with multiple copies of dhfr were selected by growing in increasing concentrations of methotrexate, and the expression of MAG by individual transfected CHO cell lines characterized as described in Mukhopadhyay et al, Neuron, 13, pp. 757-67 (1994), which is incorporated herein by reference.
  • dhfr dihydrofolate reductase
  • CHO-MAG2 The MAG- expressing transfected CHO cell line
  • ATCC American Type Culture Collection
  • ATCC CRL-12145 ATCC accession number designated; ATCC CRL-12145. All restrictions on the availability to the public of the above ATCC deposit will be irrevocably removed upon the granting of a patent on this application.
  • the neurite outgrowth on myelin or on transfected CHO cells was as described (Mukhopadhyay et al, 1994; Cai et al., 1999) with the following modifications.
  • the neurite outgrowth assay was carried out by adding 5 x 10 4 neurons to the immobilized myelin substrate or 2 x 10 4 neurons to the CHO cell monolayers. Briefly, confluent monolayers of control and MAG-expressing CHO cells were established over a 24-hour (h) period in individual chambers of an 8-well tissue culture slide (Lab-Tek). Co-cultures were established as described previously (Doherty et al, Nature. 343, pp. 464-66 (1990); Neuron, 5, pp.
  • test agents dibutyryl cAMP (dbcAMP) at 1 mM in the presence or absence of the inhibitor of transcription, 5,6-dichloro-l-b-D-ribofuranosyl- benzimidazole (DRB) at 5 ⁇ M (Zandomeni et al., 1983), were added to a culture throughout the co-culture period or monolayers were incubated with agents for one hour before adding the neuronal cell suspension and included throughout the co- culture period.
  • DRB 5,6-dichloro-l-b-D-ribofuranosyl- benzimidazole
  • DFMO DL-a- difluoromethyl-ornithine hydrochloride
  • the cells were then blocked for 30 min with DMEM containing 10% FCS and incubated for 2 hrs with a rabbit polyclonal antibody against the neuronal marker GAP43 (1:4000) (provided by G.P. Wilkin; see Curtis et al, J. Neurocvtology. 22, pp. 39-50 (1993); GAP 43-specific monoclonal antibodies are available from Boehringher
  • the length of the longest neurite for each GAP43- positive neuron for the first 180-200 neurons encountered when scanning the slide in a systematic manner was determined using an Oncor image analysis program. The same effects were obtained when total processes rather than the longest neurite was measured. For adenovirus infected neurons, only those neurons that were both GAP43 and GFP-positive were measured. Neurite measurements were compared between groups using a one-way analysis of variance (ANOVA).
  • neuron-specific antibodies such as anti- neurofilament monoclonal antibodies, which are commercially available (e.g., Boehringher Mannheim, Sigma Immunochemicals), may be used starting at dilutions recommended by the manufacturer.
  • the appropriate species-specific, biotinylated anti- Ig secondary antibody is then selected according to the species in which the primary anti-neural antibody was generated.
  • various vital dyes e.g., Molecular Probes, Oregon
  • stain neurites may be used in this assay in place of a fluorescent neural-specific antibody.
  • RNA and protein was extracted from primed neurons. The extracted RNA was used as a template for reverse transcription and PCR amplification using primers specific for the gene encoding the enzyme arginase I ("Arg I"), an isoform of arginase abundant in liver tissue but barely detectable in other tissues.
  • Arg I arginase I
  • Total RNA was isolated from 2x10 ⁇ neurons, (some of which were treated with BDNF at 200ng/ml or dbcAMP at lmM overnight) using RNeasyTM kit (Qiagen) following the manufacturers' instructions.
  • cDNA was synthesized from total RNA by priming with random hexamers and adding reverse transcriptional enzyme (Stratagene) at 37 ⁇ 0 for 2 hr. After that, Argl cDNA was amplified with Arg I-specific primers (see below) by polymerase chain reaction (PCR). The primers were obtained from GibcoBRL.
  • Peripheral (sciatic) nerve transection and isolation of DRG from rats was performed essentially as described previously in Zhou, X.F. et al., J. Neuroscl. 16, pp. 2901-2911 (1996) (incorporated herein by reference). Left-side sciatic nerve was transected at the mid-thigh level in PI 8 rats (Harlan Sprague Dawley).
  • Example 4 Ectopic Expression Of Arginase In Cerebellar Neurons
  • the adenovirus system exemplified herein involves a new generation of adenoviruses in which the El and E3 early regions have been deleted. This provides room for insertion of an expression cassette of a gene or genes up to 7.5 kB in length. (Berkner, K.L, Biotechniques. 6, pp.616-629 (1988); Massie, B et al, Cvtotechnology. 28, pp. 53-64 (1998b); which are incorporated herein by reference).
  • the adenovirus has great potential use in neurons. The virus enters the cell but cannot replicate because the essential early El genes are absent. Adenovirus remains epichromosomal in all known cells except eggs and therefore expression differences and other biological effects due to random integration into the host chromosome are not of concern.
  • Adenoviral recombinants were generated by in vivo homologous recombination in QBI-293 A cells (Qbiogene, Montreal, Canada). Insertion of DNA by homologous recombination is the most efficient way of introducing a gene into AdV because the genome is too large (36 kb) to be easily manipulated. The in vivo recombination between the two DNA molecules yields recombinant infectious viruses. The plaque purified virus is amplified on 293 cells followed by double CsCl 2 gradient purification and viral particle titration. An adenovirus lacking arginase I and including GFP cDNA was made to use as a control.
  • Cerebellar neurons were infected with the Ad-GFP or Ad-GFP/Argl. Neurons were plated at a density of 0.5 - 1.0 x 10 6 cells per 6 cm culture plates (Corning Glass Works, Corning, NY, USA). Subconfluent cells were exposed to various multiplicities of infection (MOIs) of adenoviral vectors in serum-free medium. After 4 hours, fetal bovine serum was added (final concentration, 10%; GTBCO), and the incubation continued for an additional 18 hours before assays of neurite outgrowth were performed. Preparation of lvsates and immunoblot analysis
  • Lysates were centrifuged at 15,000 RPM at 4 degrees centigrade for 30 minutes. The clear cytosol was separated from the insoluble pellet fraction and immediately used for immunoblot. The supernatants were removed carefully and the protein concentration was quantified by the Bradford method. Lysates were mixed with boiling Laemmli's buffer (lx is 100 mM Tris-HCl, pH 6.8, 4% SDS, 200 mM dithiothreitol, 20% glycerol, 2% SDS, 0.2% bromophenol blue, 10 micrograms/ml aprotinin, 10 micrograms/ml leupeptin). The samples were boiled for 10 minutes at 100° C and centrifuged at 15,000 rpm for 10 seconds.
  • Laemmli's buffer laemmli's buffer
  • Arginase activity was performed on lysates of cells that had been infected with the adenovirus-arginase I vector for 24 hours. Cultured cells were lysed in 0.1% Triton X-100 containing 2 mM Pefabloc, 2 micrograms/ml pepstatin A, and 10 micrograms/ml leupeptin. Lysates were centrifuged at 12,000 x g for 10 min, and supernatants were collected for arginase activity assays. Protein concentration was determined by the bicinchoninic acid assay (Pierce).
  • Arginase activity in cell lysates was determined by monitoring the . conversion of [guanidino- 14 C] arginine to [ 14 C] urea, using a combination of the methods of Ruegg and Russel (Ruegg, UT and Russell, AS. A rapid and sensitive assay for arginase. Anal Biochem.. 102, pp. 206-212 (1980)); and Cederbaum and Spector (Cederbaum, SD, and Spector, EB Arginase activity in fibroblasts. Am. J. Hum. Genet.. Jan 30(1), pp. 91-92 (1978)), each of which is incorporated herein by reference.
  • arginase activity assays See also arginase activity assays in, e.g., Esch et al, J. Neuroscl. 18, pp. 4083-4095 (1998); Wu and Meninger, Am. J. Physiol. Heart Circ Physiol. 265, pp. H1965-H1971 (1993), each of which is incorporated herein by reference).
  • Adenovirus-infected neurons could be distinguished by their expression of green fluorescent protein (GFP) marker.
  • GFP green fluorescent protein
  • the GFP marker is visualized using standard fluorescence microscopy techniques. GFP fluoresces green when illuminated by 488 nm light. The emitted fluorescence is detected using a 505 long band pass emission filter. The fluorescence can be detected by eye or using an image intensification camera, an analog to digital converter and standard image processing software. (Current Protocols in Neuroscience, Volume 1, Crawley et al, eds, John Wiley and Sons, publisher, 1997). We viewed the cells through a fluorescent microscope with a fluorescent filter at 510 nm.
  • GFP-positive neurons were distinguished from glial cells, which are also infected by adenovirus, by immunostaining with GAP43 (See Figure 9).
  • the transfected CHO cell assay described in Example 1 may be used to screen and identify agents that alter neurite growth properties of a particular neuronal cell type and age in a myelin- or MAG-dependent fashion. This assay may be used to test other putative arginase, putrescine and putrescine-derived polyamine modulatory agents by including them in the co-culture and measuring their effect in the presence and absence of cell-surface MAG or myelin, as described above (Example 1).
  • arginase activity in neurons may be achieved in a variety of ways that will be apparent to those of skill in the art.
  • Arginase small molecule activators will be useful according to the invention (supra) and are known to those of skill in the art.
  • New arginase inhibitors can be readily identified using routine enzymatic or other assays for arginase biological activity.
  • the activation or enhancement of arginase activity in neurons may be achieved by gene transfer techniques.
  • Arginase polynucleotides which are capable upon expression of elevating arginase activity in a cell of the nervous system may be transferred into such a cell directly. Arginase overexpression will raise ornithine and thus putrescine and putrescine-derived polyamine levels in the fluids which bathe the cells of the nervous system, e.g., the CSF, which can then be transported into cells in communication with those fluids.
  • genes that regulate the expression of arginase in cells of the nervous system, and preferably in neuronal cells may be used to modulate transcriptional activity of the arginase gene. Inducible and other regulated expression of arginase . polynucleotides is contemplated to be within the scope of this invention using known and available transcription control sequences and expression systems for regulating heterologous genes.
  • Opposite biological effects from those demonstrated herein may be desirable under certain situations, such as controlled neuronal or axonal growth guidance in the presence of neuronal growth activators. Such effects may be achieved in a neuron by blocking cAMP signaling, arginase I activity or the formation of putrescine and putrescine-derived polyamines.
  • One way to accomplish this is to inhibit protein kinase A (PKA) catalytic subunits with molecules that can bind to PKA ATP binding sites.
  • PKA protein kinase A
  • Inhibitors that compete for ATP binding have been described and will be useful for such purposes. They include H89 (5 ⁇ M) (Chijiwa et al, J. Biol Chem.. 265, pp.
  • PKA regulatory subunit inhibitors e.g., Rp-cAMP (20 ⁇ M)
  • Rp-cAMP 20 ⁇ M
  • DFMO (1 mM) is a non-toxic, specific, irreversible inhibitor of ornithine decarboxylase (ODC) which releases a conjugated imine that binds to ODC and thereby inhibits its catalytic activity.
  • ODC ornithine decarboxylase

Abstract

L'invention concerne une nouvelle identification de l'arginase en tant qu'enzyme dont l'activité peut inverser l'inhibition de la régénération neuronale au sein du système nerveux central et périphérique. Elle concerne en outre des analyses permettant de contrôler les effets de différents agents sur l'expression génétique de l'arginase et par conséquent sur la régénération et la réparation neuronales et d'identifier les agents qui bloqueront ou qui favoriseront les effets inhibiteurs sur l'excroissance neuronale. Cette invention concerne également des compositions et des méthodes utilisant des agents qui peuvent inverser les effets inhibiteurs de la myéline sur la régénération neuronale en agissant sur l'activité de l'arginase ou sur les taux de putrescine ou de dérivés de polyamine dans un neurone. L'invention concerne en outre des méthodes de régulation et de stimulation (ou répression ) de la croissance neuronale ou de la régénération dans le système nerveux, des méthodes de traitement des lésions ou dégradations du tissu nerveux ou des neurones, et des méthodes de traitement de la dégénérescence en rapport avec des états, troubles ou maladies, lesdites méthodes consistant à administrer au moins une des compositions selon l'invention.
PCT/US2001/014364 2000-05-05 2001-05-04 Methodes de stimulation de la regeneration et de la reparation du systeme nerveux par regulation de l'activite de l'arginase 1 et de la synthese des polyamines WO2001085981A2 (fr)

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EP1904092A4 (fr) * 2005-07-21 2011-08-17 Buck Inst For Age Res Facteur de croissance des fibroblastes 2 favorisant la neurogenese et la neuroprotection et prolongeant la survie dans la maladie de huntington
US8367615B2 (en) 2006-03-30 2013-02-05 Research Foundation Of City University Of New York Stimulation of neuron regeneration by secretory leukocyte protease inhibitor
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US8673594B2 (en) 2014-03-18
EP1278537B1 (fr) 2009-01-14
HK1054680A1 (zh) 2003-12-12
WO2001085981A3 (fr) 2002-03-14
EP1278537A2 (fr) 2003-01-29
US7741310B2 (en) 2010-06-22
ATE420656T1 (de) 2009-01-15
AU2001259453B2 (en) 2006-08-31
DE60137414D1 (de) 2009-03-05
ES2322332T3 (es) 2009-06-19
AU5945301A (en) 2001-11-20
CA2408255A1 (fr) 2001-11-15
US20100216710A1 (en) 2010-08-26

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